MINERALOGY OF BEACH SANDS

BETWEEN HALFMOON AND MONTEREY BAYS,

CALIFORNIA

By C. OSBORNE HUTTON

School of Mineral Sciences
Stanford University

Special Report 59

CALIFORNIA DIVISION OF MINES
FERRY BUILDING, SAN FRANCISCO, 1959

STATE OF CALIFORNIA
EDMUND G. BROWN, Governor

DEPARTMENT OF NATURAL RESOURCES

(DeWITT NELSON, Director

DIVISION OF MINES
GORDON B. OAKESHOTT, Chief

Special Report 59
Price 50£

CONTENTS Page
Introduction 7

Distribution and nature of sands 7

Electromagnetic fractionation 12

Mineralogy of the heavy minerals 12

Amphibole group 12

Tremolite-actinolite 12

Glaucophanic amphiboles 13

Hornblendes 13

Anatase 14

Andalusite 14

Apatite 14

Aragonite 14

Barite 14

Biotite 15

Brookite 16

Cassiterite 16

Chlorite 16

Chromite (see opaque minerals) : 16

Chrysoberyl 16

Clinozoisite-epidote 16

Composite particles 17

Corundum 17

Diamond 17

Dufrenite 17

Garnet 18

Glauconite 19

Gold 19

Leucoxenic material 19

Magnesite 19

Monazite 19

Olivine .20

Opaque constituents 20

Pumpellyite 22

Pyroxenes 23

Rutile 25

Sphene 25

Tantalite 26

Thorite, uranoan 26

Topaz 29

Tourmaline 29

Vesuvianite 30

Xenotime 30

Zircon 30

Doubtful identifications 30

Provenance 31

References 32

(3)

Illustrations Page

Figure 1. Index map showing localities mentioned in this report 8

Figure 2. Histograms of sands and heavy residues therein 9

Figure 3. Variation of mineral frequencies in sands from Princeton, San Mateo County,

to Pacific Grove, Monterey County 11

Figure 4. Typical crystals and fragments of pyroxenes 24

Figure 5. Typical habit and form of detrital uranoan thorite 28

Table 1. Mineral frequencies 10

Table 2. Analyses of biotite 15

Table 3. Recalculation of biotite analysis 15

Table 4. Physical properties of garnet 18

Table 5. Analyses and optical properties of monazite 20

Table 6. Recalculation of analysis of Afio Nuevo Creek monazite 20

Table 7. Spectrographic analysis of Pacific Grove monazite 20

Table 8. Powder patterns of euxenite 22

Table 9. Analyses of uranoan thorite 27

Table 10. Recalculation of thorite analyses on the basis of 16 oxygen atoms per unit-cell 29

Table 11. Effect of heating on physical properties of Ano Nuevo thorite 29

Table 12. Powder pattern of uranoan thorite after being heated in air to 860° C. for 4 hours 29

Table 13. Mineral frequencies in heavy residues from brown sandstones of the Merced

formation 31

(4)

ABSTRACT

A study has been made of the nature of the heavy mineral assemblages in beach
sands on a strip of the California coast from the north end of Halfmoon Bay to Pacific
Grove, south end of Monterey Bay. Although samples were collected over a three-year
period and at different seasons, specimens obtained from any specific locality at differ-
ent times were not found to vary significantly, one from another.

The methods used in fractionation of heavy minerals from crude sands included
elutriation, flotation in heavy liquids, electromagnetic and centrifuge separation and
hand-picking. Electromagnetic work has provided a considerable amount of data on
magnetic susceptibility of a range of minerals of known composition.

In all, 35 minerals or mineral groups have been recognized by determination of
physical properties and/or chemical composition. Among these, perhaps, the most
interesting from a purely mineralogical point of view are cassiterite, chrysoberyl, dia-
mond, dufrenite, monazite, pyroxenes and amphiboles that display most remarkable
etch features, euxenite, tantalite, and uranoan thorite. Complete chemical analyses
of biotite, monazite, and thorite have been made and are discussed in relation to their
structural formulae and physical properties; from the Pb/Th,U ratios in monazite and
thorite, tentative ages have been calculated. An age of 106 X 10 G years, approxi-
mately mid-Cretaceous, has been determined for the monazite that is clearly derived
from the granitic rocks at Monterey.

The recognition of the nature of non-translucent mineral particles has proved diffi-
cult, but magnetic fractionation has been helpful, and inspection in oblique illumina-
tion with a wide field binocular microscope is absolutely necessary. Of considerable
value were chromatographic techniques, use of alpha-ray track plates, and the NaF-
NaoCO.j fusion mixture for detection of uranium-bearing minerals.

A complete study of the problems of provinance has not been attempted at this
stage, but it is pertinent to say that, in most instances, the heavy minerals in the beach
sands have been derived from plutonic intrusives, sediments, and associated submarine
lavas and tuffs that make up the drainage area of streams that reach the Pacific Ocean
in this locality. The source of thorite, chrysoberyl, euxenite, and tantalite, all minor
or rare constituents, has not been determined.

(5)

MINERALOGY OF BEACH SANDS
BETWEEN HALFMOON AND
MONTEREY BAYS, CALIFORNIA

By C. Osborne Hutton

INTRODUCTION

This work was undertaken primarily to determine
the nature of the minerals in blacksand paystreaks
(concentrations of dark minerals in minor beds, lenses,
or irregular layers), the composition of the heavy min-
erals in average beachsands, and subsequently to deter-
mine the distribution of such constituents along a
section of the central California coastline.

Acknowledgements. The writer would like to express
appreciation for the opportunities for research provided
by the Raw Materials Division, Atomic Energy Com-
mission's Contract AT (30-1) -11 17, and to facilities made
available by and through that organization. To Mrs.
Muriel Mathez, Dr. P. Merritt and Dr. F. G. Tickell,
sincere thanks are tendered for assistance in many ways
at various times, and to Professor Adolf Pabst, Uni-
versity of California for the X-ray diffraction pattern
of euxenite.

DISTRIBUTION AND NATURE OF SANDS

Sands were collected from many localities between the
north end of Princeton Beach, San Mateo County, Santa
Cruz, Santa Cruz County, and Pacific Grove, Monterey
County, at the south end of Monterey Bay (see figure
1). Forty-nine samples of blacksand paystreaks from
17 localities, and 86 typical sands from these and other
localities were collected along the coastline. Blacksands
are relatively numerous, nowhere show great lateral
extent or depth, and in many places are only transient.
Storm conditions appear to favor active concentration
of the heavier constituents in these sands. However,
some blacksand concentrations appear to be relatively
stable. They are particularly well developed in the
following localities: Princeton Beach just south of the
pier, south side of the mouths of Tunitas, San Gregorio,
Ano Nuevo Creeks, south of Pigeon Point Lighthouse
(rocky shoreline with shallow depth of sand), several
points east of Ano Nuevo Point, and at many points
between Pajaro River and Moss Landing in Monterey
Bay. Paystreaks that occur between the mouth of
Salinas River and Monterey appear to have a stability
of an intermediate character. The presence of a head-

land or river effluence immediately to the north of black-
sands is common and these obstructions, by altering the
direction of southward-moving ocean currents, or by
reducing velocity, have permitted deposition of the heav-
ier part of the sedimentary load, in localities where
blacksands are especially well developed, such as the
mouth of Tunitas Creek, plentiful driftwood makes
post-hole sampling difficult.

Although grains of specific minerals may exhibit a
high degree of roundness and polish, the constituents
of the sands generally are angular, with quartz and
feldspars particularly so. The average grain size does
not vary notably from place to place and most of the
sands may be classified as medium-grained or fine-
grained (Wentworth, 1922). Blacksands tend to be finer
grained than sands showing little accessory mineral con-
centration, but the ratio of heavy minerals to light in-
creases notably with decrease in grain diameter (figure
2). This is particularly evident in the very fine-grade
and silt fractions, since they are made up almost en-
tirely of heavy minerals, but such fractions rarely make
up more than a few percent of the total sample.

Where winds have selectively removed low specific
gravity minerals from sand, the grain size of the thin
veneer or residue of heavy constituents that remains
as blacksand is very much finer than that of light-colored
surrounding sand on which the winnowing process is
not far advanced. Although the products of the win-
nowing action of prevailing on-shore winds are quite
evident at many points on the coastline they are of
small volume; production of larger quantities of black-
sand by these means was observed particularly in the
sand-dunes both to the north and south of the mouth of
Pajaro River.

The relative frequencies of the heavy minerals present
in a number of representative assemblages after re-
moval of magnetite and ilmenite are shown in table 1
and, by and large, these data are averages of counts of
at least 300 grains for each of several preparations from
specific localities. For example, the data recorded under
" Whitehouse Creek" have been obtained by averaging
counts of a total of 400 grains in each of three size-
fractions of eight samples from that locality, that were

(7)

CALIFORNIA DIVISION OP MINES

[Special Report 59

50'

40'

Iff

37°00'

50'

pt. Lobos

Pt. San Ped ro

90°

Bolsa Pt.>

G a z o s C r.
Whitehouse Cr.

Ano Nuevo Pt

DAVENPORT,

LOCALITY MAP

MOSS LANDING

/
Salinas R.

Scale of Miles

6 4 2

40'

Pacific Gr,

ONTEREY

30'

20'

10'

I22°00'

50'

Figure 1. Index map of coastline from Golden Gate to Pacific Grove, Monterey peninsula, showing localities specifically mentioned

in this report.

1959]

MINERALOGY OF BEACH SANDS

collected over a period of 2 years. But for the finest
screenings of Whitehouse Creek material, — 250 mesh,
fewer than 100 mineral grains remained in each case
after removal of ferromagnetic (magnetite) and strong-
ly paramagnetic (ilmenite) fractions; hence counts of
any significance were not possible. Where at least 300
grains were available for counting, the percentages of
the different minerals thus obtained have been expressed
in table 1 following the procedure of Evans, Hayman,
and Majeed (1934). However, where the number of
particles is inadequate to permit satisfactory use of
this scale the following system is used:

p = predominant (> 60 percent)

a = abundant (20-59 percent)
fa = fairly abundant (5-19 percent)
m = minor constituent (< 4 percent)

r = rare.

Many samples from localities other than those listed in
table 1 were studied, but the grain counts from these
have not been included in this table since they add little
if anything to the general picture set out in table 1
and figure 3. Magnetite and ilmenite make up much of
the heavy fractions and ilmenite, which tends to have
larger average grain-diameters than magnetite, is the
more abundant constituent in most samples.

-i — I — i — I — r

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t I i I r

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_60
_40

TOTAL FRACTION.

HEAVY RESIDUE.

IOO

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20 rn

100 £

80 CD

60 m
m

20 N
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100 o

80 £

60
40
20

FlGUBE 2. Histograms of sands and heavy minerals therein. (1) Princeton Beach; (2) Mouth of Tunitas Creek; (3) Mouth of San
Gregorio Creek ; (4) Mouth of Butano Creek ; (5) Mouth of Bolsa Creek ; (6) Mouth of Gazos Creek ; (7) Mouth of Whitehouse
Creek; (8) Mouth of Ano Nuevo Creek; (9) Aptos Beach; (10) Mouth of Pajaro River; (11) Marina Beach; (12) Monterey;

(13) Pacific Grove.

CALIFORNIA DIVISION OP MINES

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MINERALOGY OP BEACH SANDS

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CALIFORNIA DIVISION OF MINES

[Special Report 59

The li*rlit fractions, material with specific gravities
less than about 2.88, consist mainly of feldspars, quartz,
acid volcanic glass, glauconite (this is found in heavy
fractions as well), calcite, composite rock fragments,
clay pellets, micas, fragments of both calcareous and
siliceous organic remains, and a minor amount of non-
mineral matter. Detailed investigation of this material
has not been made.

Variation of mineral frequencies, exclusive of those
for ilmenite and magnetite, is illustrated in figure 3
which shows the following points:

(1) The effect of introduction of fine-grained augite from the
Purisiraa formation.

(2) Changes due to accession of material from San Lorenzo
River that enters the ocean at Santa Cruz just north of
Aptos.

(3) Marked change of character of sands south of Salinas River.

ELECTROMAGNETIC FRACTIONATION

Provided the diameter of particles in samples is uni-
form, the magnetic susceptibility of the particles de-
pends largely on composition. Ironstain on the surface
of mineral grains can have considerable effect on their
behavior in a magnetic field, and on many occasions,
stains on some grains and not on others have permitted
selective attraction and concentration, after which the
stain has been removed by chemical means. Thus it has
become standard practice not to remove ironstain unless,
of course, it is excessive, until the last possible moment.
Artificial production and selective deposition of metallic
iron films on mineral grains followed by electromagnetic
fractionation has been utilized in some instances (Vin-
cent, 1951, p. 1074).

The Frantz separator was usually adjusted with a
slope of 15° and a tilt of 10°, but before separations
were made with it, ferro-magnetic material was removed
with a hand electromagnet (Hutton, 1950, p. 644).

The relative order of fractionation of a number of
constituents with a particle size range of — 0.124 -(-0.061
mm, follows, but excluded are data on several minerals
for which there was too small an amount of material for
experimentation :

Fraction 1. Current 0.2 amps:

(a) Ilmenite, martitized magnetite, and other oxides of iron

with or without titanium ; often heterogeneous in nature,
(h) Iron-rich chrome spinels,
(e) Silicates, chiefly pyroxenes and aniphilioles that contain

inclusions of magnetite, ilmenite, etc.

(d) Composite particles.

(e) Iron-rich epidote and allanite (FesOs, 10.25 percent; FeO,
7.:V.'> percent; MnO, 0.74 percent; ThCK, 0.95 percent). Al-
though only dubiously recognized as constituents of the
sands studied, members of the colnmbite-tantalite series
are attracted at about 0.25 amps. ; samarskite is attracted
at approximately 0.275 amps.

Fraction 2. Current at 0.35 amps:
(a) Chromite.
(1>) Less ilmenite than at 0.2 amps.

(d) Pyroxenes, chiefly augite and hypersthene ; olivine with
15-20 percent of the fayalite molecule.

(e) Epidote, garnet (spessartite-almandine ; » = 1.70-1.80; sp.

I»r. = about 4.1. chrysoberyl, presence possibly due to
inclusions, and inclusion-bearing monazite.

(f) Euxenite; other studies by the writer have shown that
members of the euxenite-polycrase, and aeschynite-priorite
groups generally, are attracted at 0.35 amps., or very
close thereto, although a sample of blomstrandine from
Morefjaer, Arendal, Norway was concentrated precisely at
0.31 amps.

(g) Composites.

Fraction 3. Current at 0.45 amps :

(a) Main pyroxene concentrate (composition of the common
pyroxene is approximately equivalent to that of augite
close to diopside as determined from optical measurements,
viz: Wo 49 percent, En 38 percent, Fs 13 percent).

(b) Garnet (spessartite-almandine).

(d) Sphene, monazite, pumpellyite, xenotime.

(e) Minor opaque minerals.

(f) Zircon by reason of inclusions therein.

Fraction 4. Current at 0.75 amps :

(a) Main monazite and sphene fractions. Monazite contained
Th0 2 4.22 percent ; FeO 0.61 percent ; sphene with AI2O3
1.44 percent and total iron as FeO 1.23 percent was at-
tracted at 0.60 amps., rejected at 0.55 amps.

(b) Considerable amount of uranoan thorite; dark-colored
phase.

(d) Zircon by reason of inclusions.

(e) Pyroxenes, amphiboles, opaques, epidotes, all in minor
amount.

(f) Composites abundant in specific instances (saussuritic ag-
gregates, etc.).

Fraction 5. Current at 1.2 amps :

(a) Sphene important but less abundant than in fraction 4.

(b) Zircon with minute inclusions.

(d) Grossular, hydrogrossular.

(e) Composites very important in some samples.

(f) Opaque fragments usually rare.

(g) Corundum; andalusite, but erratic in behavior due to fre-
quency of opaque inclusions.

Fraction 6. Fraction rejected at 1.2 amps:

(a) Zircon and apatite are usually the dominant constituents
here.

(b) Pale green uranoan thorite.

MINERALOGY OF THE HEAVY MINERALS

Amphibole Group

At least one member of the amphibole group is pres-
ent in each size fraction of each of the sands studied,
although three and even four varieties have been found
in many samples. Amphiboles recognized are derived
from at least two distinct paragenetic associations :
tremolite-actinolite and glaucophane from a metamorphic
environment, and brown and oxy-types with which may
possibly be grouped a green to brownish-green horn-
blende, derived from volcanic, or certainly igneous
sources. In general the frequency of amphiboles present
in the sands shows considerable variation from north to
south along the coastline studied and, in general, mem-
bers of the group are only slightly more abundant in
coarser than in finer grade sizes.

Tremolite- Actinolite

Members of this group are rare and occur as minute
needle-shaped or ragged fragments of very pale green to
bluish-green color with faint pleoehroism. For one sam-
ple, a — 32 -f- 60 fraction from a blacksand paystreak
three-quarters of a mile south of the mouth of Pajaro
River, the following optical data were recorded :

a= 1.627
y = 1.649

X = very pale green
Z = pale bluish green
Z A c = 18°
2V = 65° (-)

1959]

MINERALOGY OP BEACH SANDS

The extinction angle Z' to c for -what seemed to be
fragments resting on (110) was approximately 22°. a
value in excess of that found for the (010) plane or the
true extinction angle Z to c. On the basis of Fresnel's
law the extinction angle for an orientation parallel to a
cleavage plane when Z to c and 2V are 18° and 65° re-
spectively, was found by construction (Duparc and
Pearce, 1907) to be 21°. Accordingly it must be stressed
that determination of extinction angles must be made
with some caution when orientation within the zone
[001] is not known exactly. The blue tint in the Z ■ —
vibration direction suggests that this amphibole is a
member of the actinolite-glaucophane series of Kunitz
(1930), but close to the actinolite end since a lavender
tint is not evident.

Glaucophanic Amphiboles

Amphiboles that belong to the glaucophane-riebeckite
rather than to the actinolite-glaucophane series are fairly
widely distributed but in none of the samples examined
do they exceed 1 percent of any particular size fraction,
and quantity is usually much less than this.

An abraded, but dominantly stumpy, prismatic form
is general. Pleochroism with X = colorless, flecked with
green, Y = violet, and Z = deep azure blue is usual in
spite of variation in other optical properties. Separation
of sufficient material for more complete determination
was not accomplished except once when the following
data were obtained: a = 1.635 ± 0.002; y = 1.649;
Y — a = 0.014; 2V = 12° (— ) ; ZAc = 4° ; dispersion
r < v strong. The type of dispersion was not recognized
with any degree of certainty but the positions of the
colored areas in the interference figure relative to the
points of the melatopes suggest dispersion of bisectrices,
rather than of optic axes. The size of the optic axial
angle points to a composition close to crossite, but the
amphibole is not that since optic axial plane and clino-
pinacoid are parallel. Optic axial angles larger than 30
to 50° appear to be more usual, however, and zoned crys-
tals with lighter colored central areas and darker periph-
eries are not uncommon.

Inclusions are frequent and the following were rec-
ognized : quartz, plagioclase (most likely albite), mem-
bers of the clinozoisite-epidote group, muscovite, stilp-
nomelane, sphene, pumpellyite ( ?), apatite; some opaque
grains were found, enhancing the magnetic susceptibil-
ity of the particles.

Hornblendes

Three distinct varieties of hornblende are present:
green, brown, and oxy-types. In general, green varieties
are dominant, and brown and oxy- forms much less
abundant. Well-rounded particles are particularly com-
mon in coarser grained fractions, whereas cleavage frag-
ments with ragged terminations or otherwise irregularly
fractured grains are decidedly dominant in the finer,
and especially in the finest, grade sizes.

In general terms, hornblendes are attracted at lower
field strengths than are pyroxenes, particularly clino-
pyroxenes, but not always, since pyroxene crystals and
fragments are more often contaminated with opaque
oxides than are hornblendes. This is particularly true
of the - — 115 -j-250 fraction from the mouth of Gazos

Creek where both clinopyroxenes and hypersthene make
up approximately 50 percent of the ilmenite fraction
attracted in a weak magnetic field (0.10 amps.). In ma-
terial collected from a point just south of Pajaro River,
both pyroxenes and amphiboles were so contaminated
with inclusions of magnetite or ilmenite that they were
fractionated together with magnetite in the ferromag-
netic portion and also with ilmenite in a slightly stronger
field. For crystals devoid of opaque ferruginous and or
titaniferous inclusions, however, pyroxenes are magneti-
cally less susceptible than amphiboles.

In general, inclusions are less frequent in hornblendes
than in pyroxenes and where identification could be
made they were: iron oxides (magnetite, titanomagne-
tite, ilmenite, hematite), apatite, quartz, plagioclase, leu-
coxene (?), and needles of rutile (?).

Solution effects have hampered development of
grains with multiple terminating pyramids — the so-
called "cockscomb" structures of Ross et al. (1929) and
other investigators ; in fact, they are decidedly rare com-
pared to similar effects produced in the associated ortho-
rhombic and monoclinic pyroxenes.

Green or Greenish-Brown Amphiboles. Amphiboles
belonging to this category are more important constitu-
ents of blacksands, paystreaks, and heavy fractions than
the sum of other varieties present. In material from
Princeton Beach, green or greenish-brown hornblendes
constituted 60 percent of the — 60 +115 fraction, and
percentages in excess of 20 are not uncommon in other
samples. No size fraction of any sample studied is free
from hornblende of this category.

Optical properties show a range of values and the data
that follow give some measure of this :

Mouth of Ano

f mile south of

Range or other

Nuevo Creek

Pajaro River

data noted

1.654

1.650

1.650-1.662

1.672

1.665

1.665-1.679

— a

0.018

0.015

0.014-0.022

ZAc

19°

17°

14-22°

yellowish -green

pale green

yellow

olive-green

green

brownish-green

deep green with

deep green

deep brownish-

a tinge of blue

green (rarely
nearly opaque)

Absorption : Z >Y >X

Z>Y>X

In some instances green to greenish-brown hornblendes
are so deeply colored that they are nearly opaque for
the — 60 +115 size fraction, and at first sight, these
grains differ little from ilmenite when they are viewed in
oblique illumination. This is especially so if fragments
are well rounded and polished so that prismatic cleavage
is not evident.

Undoubted solution effects comparable to those devel-
oped in pyroxenes are infrequently found (see Princeton
— 115 -|-250 mesh where incipient pyramidal termina-
tions have developed). Zoning due to pre-depositional
circumstances was noted in occasional grains, and gen-
erally this takes the form of dark green nuclear areas
with paler colored or colorless peripheral zones.

Brown amphiboles, generally less abundant than are
green varieties, exhibit a range of forms similar to those
of the latter, and show complete gradation towards them
optically. In a number of instances, as in brown varieties
devoid of any reddish tints, pleochroism is not as pro-
nounced as in green hornblendes.

CALIFORNIA DIVISION OF MINES

[Special Keport 59

Oxy -Hornblendes. Red-brown amphiboles of the oxy-
hornblende type are present in most size fractions but
in no instance exceed 41 percent of any fraction and
usually are very much less than this. They exhibit a
range of forms similar to those found for green and
brown amphiboles. Color is typically red-brown and op-
tical data for a wide range of fragments are as follows :

X = brown, yellowish-brown, golden brown.

Y = deep brown.

Z = deep red-brown.
Z > Y > X
2V = 59 — 73° (— )

ZAc: 2 — 7°, but usually closer to the lower figure
(Fedorov stage determinations).

a 1.675*- 1.678

Y 1.740*- 1.747
y-a 0.062 -0.069

Anatase

Anatase, recognized as a rare constituent of the finest
fraction of blacksand found at the mouth of Afio Nuevo
Creek, occurs as pale yellow, non-dichroic, rectangular,
fractured tablets that exhibit a pattern of parallel
striations.

Andalusite

Very well rounded (Princeton) to highly irregular
grains (Whitehouse Creek) of andalusite were found
in a number of samples, but this constituent is never
more than a minor accessory. Inclusions are visually
quite numerous, with both opaque and brownish iron
oxides predominant but biotite common, whereas in other
samples extensive sieving with quartz, feldspar, or bio-
tite was noted. Pleochroism is pronounced and in larger
sized fragments, as in the — 32 -(- 60 fraction of Tunitas
Creek sand, this characteristic is most marked. For the
Tunitas Creek example the following data have been
determined.

a = 1.633
Y = 1.644
Y — a = 0.011
X — rose
Z = green

Unfortunately adequate material for manganese and
iron determinations was not available, but the intensity
of absorption and rather higher refractive indices sug-
gest some degree of replacement of Al 3+ by Mn 3+ and/or
Fe 3+ .

Apatite

Although apatite is widely distributed, few fragments
are found in most samples, and more than 0.5 percent
was not recorded.

Stumpy euhedral prisms that exhibit effects of slight
abrasion predominate in finer grade sizes, whereas well
rounded fragments are most often met with in coarser
screenings. In many cases apatite is free from inclusions,
but when these are seen they are usually in the form of
lines of cryptocrystalline particles arranged parallel to

* These values, 0.003, were found for a large number of oxy-
type amphiboles pr< s< nt in the sands.

the vertical crystallographic axis. Such crystals have
the appearance of being medium to strongly dichroic
in smoky or brown tints, but to what extent this appar-
ent dichroism results from a "wink" effect due to
rapid change of the difference of refractive indices
between inclusions and apatite host on rotation of the
microscope stage, is not clear.

Pale yellow apatite is associated with colorless frag-
ments of the same mineral in one sample (mouth of
Aiio Nuevo Creek), and in a black sand paystreak from
the northern end of Princeton Beach, occasional extraor-
dinarily smoothed, egg-shaped grains were recognized.
The latter are colorless and water-clear with the longer
dimension of the ellipsoidal particle invariably at an
angle to the c crystallographic axis, that is, to the longer
dimension of the original crystal. Such material must
result from very long-continued abrasion of initially
irregularly shaped fragments, otherwise it is difficult to
visualize the way in which crystals of apatite of normal
habit could become worn to elliptical forms that do not
exhibit some degree of parallelism to the forms of the
original crystals. These circumstances are reminiscent
of those described for zircon from Slab Hut Dredge,
Westland, New Zealand (Hutton, 1950, p. 687).

Collophanic fragments derived from tooth and bone
material are generally irregular in shape in finer grade
sizes and rounded or much abraded in coarser par-
ticles; color is typically pale yellow but shows a range
between this and red-brown. Weak anisotropism and
cryptocrystalline aggregate structure that does not
exhibit definite extinction, are characteristic.

X-ray powder patterns are yielded by single particles
of collophane, and although films exhibit no reflections
at angles greater than 60° 2 0, the patterns are otherwise
comparable to those of apatite. Measurements in one case
gave cell dimensions of a = 9.33 A., c = 6.88 A ± 0.03 A,
or values similar to those recorded for carbonatian fluor-
apatite.

Aragonito

The orthorhombic form of calcium carbonate has been
recognized as an occasional constituent of sands from
several localities, and in each instance it forms thin,
abraded fragments with aggregate structure ; presumably
this is shell material. A distinct pleochroism, nearly
colorless to pale mauve or purple (Hutton, 1945, p.
300) is usual; however, optic axial angle determinations
of 17° and 19° in two fragments with y = 1-684 and
1.685 respectively, support diagnosis as aragonite. If
this is shell-derived material, and it certainly appears
to be so, the data recorded here do not support B0ggild's
(1930, p. 237) contention that the optical properties
of shell aragonite are not exactly identical with those
of aragonite from other natural sources.

Barite

Barite was found in four samples but only in sands
near the mouth of Pajaro River is it more than a min-
eralogical curiosity. Rectangular cleavage fragments of
dusty aspect due to clouds of innumerable minute, and
colorless indeterminate inclusions are usual. A mottled
or blotchy effect comparable to that found in barite of
concretions is evident between crossed nicols in some
instances; it may result from slight disorientation of

1959] MINERALOGY

originally parallel lamellae. An optic axial angle of
38-40° and a value of 1.635 for a supports the conclu-
sion that the mineral has a composition close to that of
pure harium sulfate.

Biotite

It is to be expected that micas would not be well
represented in mineral assemblages on exposed ocean it-
beaches but biotite has been recognized in four sands,
in which it is usually more abundant in the coarser
size fractions. A deep red-brown color with very strong
pleochroism is characteristic and, for separated platelets,
the following data have been determined :

Aptos Beach :

y. 1.656, 1.662, 1.664,

2V: 0° 0° 34°

Dispersion- - r<v, very strong.

Mouth of Butano Creek:
y: 1.660, 1.689.

In sands from Pacific Grove, biotite is much more
plentiful and deemed worth fuller study. Before analysis
the mica concentrate was carefully freed of platelets
that contained inclusions of zircon and apatite, and
absence of both zirconium and phosphorus in the spectro-
graphic analysis indicated that purification was ade-
quate. The Pacific Grove biotite (analysis 1 table 2)

Table 2. Analyses of biotite.

12 3 4 5

Si0 2 34.98 35.88 34.43 34.62 34.87

Ti0 2 3.47 4.17 3.31 2.42 3.21

A1 2 3 17.00 14.96 17.43 17.63 17.31

Fe 2 O a 0.30 2.33 2.50 4.99 6.48

FeO 14.49 20.88 21.65 18.92 17.56

MnO 0.42 0.18 0.44 trace 0.32

MgO 5.80 10.04 5.88 7.54 6.97

CaO 0.38 0.12 1.22 0.38 0.29

Na 2 0.39 0.36 0.58 3.09 0.42

K 2 7.02 9.20 8.83 7.75 8.13

H 2 O+105°O. 3.96 } n an }., _ R (2.65 3.35

H 2 0— 105-C. 1.40 f u J" 10.17 0.57

F. 0.47 1.58 1.12 1.38

99.14 100.50 100.29 100.16 100.86
Less O for F 0.19 0.66 0.47 0.58

98.95 99.84 99.82 100.16 100.28

1. Biotite from sands, Del Monte Properties, Pacific Grove. Monterey Co., California.
Analyst: Atomic Energy Commission Chemical Laboratory, analysis 4453-A. Silica
corrected for fluorine.

2. Biotite from monzodiorite, Belknap Mts. (Chapman and Williams, 1935, p 512,
Table 7, anal. no. 2).

3. Biotite from dark vein in granite, Widecombe, Dartmoor. See Nockolds, 1947, p. 406,
Table 2, anal. 17. Summation includes 0.14 percent Li 2 0.

4. Biotite from gneiss, Tomanowa Valley, Poland (Zastawniak, 1951).

5. Biotite from Jamesburg, Carmel Valley, California. Analyst: C Osborne Hutton.

is iron-rich, relatively low in magnesia, but comparable
in many respects with the micas listed in columns
2-5, inclusive, in that titanium, total iron, and alumina
are similar. In addition, the optical properties are
similar to those of the mica represented bv analvsis 2
(table 2).

Hecalculation of the biotite analvsis on the basis of the
formula (O.OH.F) 2 W(X.Y) 2 - 3 [Si 4 O 10 ] (Strunz, 1949,
p. 212), set out in table 3, makes it clear that a consider-
able amount of Al 3+ must be grouped with Si 4+ in order
to bring the tetrahedrally coordinated group to four as
is required structurally. Titanium has been included
with six-coordinated metals on the basis that the Ti 4+ —
O 2 " radius ratio is better suited to six rather than to

OF BEACH SANDS

four coordination. However it should be borne in mind
that if Ti 4+ is grouped with Si 4, in this instance, Al :1 '
would have to be adjusted to permit only 1.111 atoms to

Table .'?. Recalculation of analysis of biotite from Pacific drove.

Wt. percent Oxygen Metals
Si<> 2 34.9S 1.105 2.689, , M1 I 4.00

ma), 17.06 .502 1.544] '■;";'

Ti() 2 3.47 .087 .200 <■ — 1 "l

Fe 2 O s 9.30 .175 .536 '

FeO 14.49 .202 .931 2.591

MnO 0.42 .006 .027

MgO 5.SO .144 .004

CaO 0.38 .007 .031

Xa 2 0.39 .006 .058

K2O 7.02 .074 .688

ILO 3.96 .220 2.030 / o 144

F 0.47 .012 .114 \

This leads to the formula :

(OH,F),. 14 (K,Na,Ca). 7S (Mg,Mn,Fe 2 +,Fe 3+ ,Al,Ti)o ,

[(Si,Al)40 1? ]
enter the tetrahedrally linked sheets, the remainder in
six-coordination. The question of the position of Ti 4+ can-
not be unambiguously settled here, but it should be re-
membered that similar difficulties arise in distribution of
Ti 4+ in titaniferous augites low in Fe 3+ and Al 3+ . In such
cases where the combined Si 4t and Al 3+ is insufficient to
satisfy the requirements of pyroxene structure, there ap-
pears to be no alternative but that Ti 4+ may replace Si 4 *
(Dixon and Kennedy, 1933; Deer and Wager, 1938).

If Ti 4+ is grouped with the cations of coordination
number 6, then Al 3+ in the Pacific Grove biotite is domi-
nantly tetrahedrally linked with only a small amount
remaining to replace X and Y group cations. This divi-
sion of Al 3+ is found in biotites from igneous rocks de-
void of muscovite in which biotite tends to be the sole
mafic constituent or those in which minor hornblende
may also be present (Nockolds, 1947). Certainly the
granites which crop out in the vicinity, the source rocks
of the mica described here, may be so described, in that
they are generally devoid of muscovite and hornblende.

The figure of 0.78 for the large ions Ca 2+ , Na + , and K +
is unsatisfactory and suggests that the analytical deter-
mination of alkalis may be in error. On the other hand,
the relatively high figure for H 2 — 105° C. would tend
to suggest that the mica has undergone some alteration ;
this may also be a reason for the deficiency in the \V —
group.

Spectrographic determinations on the Monterey biotite
are as follows:

>10 percent Al, Fe, Mg, Si

1-10 Ti

0.1-1.0 Ca, K(?), Mn, Na

0.01-0.1 Ba, Pb, Zn

0.001-0.01 B, Cu, V

<0.00i Ag, Cr, Mo, Sn

Not detected As, Bi, Cd, Co, Ga, Ge, In, Ni, P,

Pt, Sb, Ta, Th, U, W, Y, Zr.

Physical properties for the analyzed biotite are :
a = 1.610 ± 6.004
Y = 1.665 ± 0.002
Y-a = 0.055
X = yellow
Y = Z dark brown
X< Y = Z

CALIFORNIA DIVISION OF MINES

[Special Report 59

Dispersion strong with r < v.

2V = — 20° ; generally 8 — 12°.

sp. gr. at 22°C. 3.04 — 3.09 ; generally 3.06

0.01

Brookite

Brookite is a rare but fairly constant constituent of
finer fractions of many sands, and is almost invariably
found concentrated in the non-magnetic fraction * as-
sociated with zircon, cassiterite, apatite, rutile, etc.

It forms equidimensional sub-euhedral to euhedral
grains that appear to be tabular parallel to (010), since
a high proportion of grains exhibit Z perpendicular
thereto (Palache et al. 1946, p. 560). Color by trans-
mitted light is pale yellow, but in oblique illumination it
is brownish-yellow with a rather waxy or greasy luster
(cf. rutile). Pleochroism is faint but distinct for orienta-
tion perpendicular to Z, with the direction perpendicular
to the striae pale yellow, and yellow parallel thereto.

In blue light 2V is small and the optic axial plane is
parallel to the striae, whereas in red light 2V is dis-
tinctly larger and the optic axial plane is perpendicular
to the c axis, assuming that the striae are parallel to
that axis.

Cassiterite

Cassiterite has been recognized with certainty in the
finer fractions of samples from Aptos Beach and the
mouth of Ano Nuevo Creek, as anhedral particles of
highly irregular shapes and pronounced conchoidal
fractures. Brown grains, with blotchy distribution of
color and weak dichroism are usual but here and there
fragments that give positive tests for tantalum with
tannin, and exhibit strong dichroism, colorless (O) to
deep blood-red (E), were found. Some twinning was de-
veloped, and in such fragments dichroism is much more
evident, owing to juxtaposition of two distinct tints
across the composition plane.

Chlorite

Chlorite was recorded as a rare accessory in three
examples and it is to be expected that individual flakes
of members of this group, as distinct from composite
grains containing chlorites, such as saussurite, schist
fragments, etc., would be poorly represented in sands
on open beaches. From the finest fraction of sand from
the mouth of Gazos Creek occasional ilakelets of pale
green, optically negative, chlorite were separated and
determined to have refractive indices very slightly less
than 1.64, but this figure was not accurately determined
owing to lack of material; however, one of the iron-rich
chlorites appears to be indicated.

Chromite

Chromite and chromian spinels will be considered
under the heading of opaque minerals.

Chrysoberyl

Sonic of the occasional colorless fragments of chryso-
beryl noted in the assemblages of sands from near the
mouth of Ano Xuevo and Butano Creeks were well
anded, others irregular with conchoidal fractures, and
her water-clear or semi-translucent owing to myriads of

l: '' '' ! amps, when the isodynamic separator is set at

a slope of 10° ar tilt of 8°.

dust-like inclusions. Rare fragments exhibit repeated
twinning with well marked striations parallel to the
periphery * ; for such crystals the following data were
Foiind: a = 1.739 ± 0.003, y = 1.747, y — a = 0.008.
These refractive indices are distinctly lower than those
recorded for chrysoberyl by Winched (1951, p. 89),
but somewhat higher than data obtained for synthetic
chrysoberyl by Geller (1941, p. 564), viz. a = 1.732,
Y = 1.741. In a fragment of a multiply twinned crystal
the optic axial angle ranged from 40-55° (-)-), whereas
in other particles 45-60° ( + ) was noted.

Clinozoisite- Epidote

Members of the epidote group are widely represented
and the Al-Fe members of the epidote series are particu-
larly common, with piedmontite rare. Zoisite is a minor
constituent but widely distributed, whereas allanite, the
only member of the allanite series recorded, is un-
common.

Epidote Series. Epidote and clinozoisite are grouped
together, owing to the difficulty of distinguishing be-
tween them when the composition is close to that of non-
ferriferous members, without recourse to time-consum-
ing refractive index determinations. Distinction is also
rendered more troublesome by notable and rapid move-
ment of the ellipsoid, movement that does not seem to be
entirely dependent on compositional change, (Johnson,
1949, pp. 506-515).-

Clinozoisite-epidote is ubiquitous in each size fraction
with slightly greater frequency in finer grade sizes.
Fragments are mainly anhedral and conchoidally frac-
tured, colorless with slate blue anomalous tints in the
finest size, but pale yellow to greenish yellow with high
order colors in coarser fragments. Pleochroism is often
evident in particles of large size, or in iron-rich varie-
ties. Refractive indices for the Y-vibration direction lie
between 1.740-1.752 in fragments tested; this is equiva-
lent to approximately 8-12'/' of Fe 2 3 in the molecule.
In the — 60 -f- 115 fraction of material from near the
mouth of Whitehouse Creek, however, rounded cleavage
fragments of clinozoisite were found with faint, but
striking pleochroism, X = pale yellow, Y = pale blue,
Z = pale yellow, Y > X = Z. These characteristics
are suggestive of pumpellyite, but other optical data
(cf. Johnson, 1949, Table 4, p. 514, last column), defi-
nitely point to clinozoisite; these are: a = 1.720,
£=1.724, y = 1.735, y — « = 0.015, 2V = 90° (±),
r < v distinct.

Inclusions are frequent and clouds of dust-like parti-
cles of iron oxides are particularly well represented in
clinozoisitic or iron-poor varieties.

Zoisite. The orthorhombic dimorph of clinozoisite is
rather widely distributed as clear colorless anhedra with
occasional inclusions of opaque oxides. These fragments
often show preferred orientation in mounting media so
that centered or very nearly centered interference figures
may be obtained therefrom.

a - zoisite, much less common than the (5 - variety, is
recognized by parallelism of the optic axial plane and
(010) cleavage, and by strong dispersion with r < v

* Comparable, to some extent, to the crystals figured by Berthois
(1935), pi. 4, tigs. 1 and 2).

1959"

MINERALOGY OF REACH SANDS

(Bolsa Point material). The |3 - variety shows ;i range
of 2V (0-20°) will) r > v. When 2V is very small,
the mineral is almost uniaxial in bine light but in red
light the optic plane is perpendicular to the cleavage
(Princeton Beach).

Allanitc: Occasional fragments of non-metamict al-
lanite were fonnd in several beach sands, but never did
it exceed 0.5 percent of any size fraction. The habit
ranges from well-rounded almost spherical forms to
sharply angular fragments with pronounced conehoidal
fracture surfaces. Prismatic crystals are not common,
but in the few instances where such forms could be
recognized, the longer dimension was determined to be
parallel to the Y vibration direction.

In each instance color is characteristically a deep
brown and pleochroism is intense as follows: X = pale
yellow, golden yellow (in thin edges) to pale yellowish
brown ; Z = very deep brown ; almost opaque. A negative
optic sign was definitely determined in two instances
(A no Nnevo, Butano), and a positive sign observed for
material in the — 60 -\- 115 fraction of sand from the
mouth of San Gregorio Creek. The size of 2V was not
readily estimated due partly to intense color but for
grains from near the mouth of Butano Creek a very
small angle, approximately 10-20°, was noted and very
pronounced dispersion was apparent.

The following data were determined for two separate
occurrences :

Aiio Nuevo Creek Butano Creek

u = 1.785 1.780

Y = 1.816 1.812

Y-ot = 0.031 0.032

Sp. Gr. (22° C.) = 3.89 ± 0.02 3.90 ± 0.02

Both samples are readily soluble in hot concentrated
IIC1, and oxidation of nitric acid solutions by bismuth-
ate indicated the presence of considerable manganese (cf.
allanite from Yosemite National Park, California, Hut-
ton, 1951).

Piedmontite: A few prismatic, pale-colored frag-
ments of the manganiferous epidote, piedmontite, were
recognized in material from near the mouth of Aho
Nuevo Creek, but elsewhere the grains are parti-colored
with pronounced zonary bands parallel to the length of
the fragments, that is, parallel to the 1) crystallographic
axis. Pleochroism is weak but distinct as follows :

X = pale yellow
Y = pale purple
Z = violet
Z ^ X ^ Y.

Birefringence, and refractive index for the Y-vibra-
tion direction, are approximately 0.015 and 1.725 respec-
tively. These data taken together with the relatively
weak absorption suggest a variety low in both Fe 3+ and

Mn 3t .

Composite Particles

Rock fragments and other mineral aggregates are
present in every sample so far studied, and in coarser
screenings they often rank among the more important
constituents and in some fractions as dominant ones. No
attempt has been made here to differentiate between

distinct varieties of composite material for counting pur-
poses, but instead any detailed identification has been
made for the sole purpose of elucidating provinance.

The following mineral associations and rocks con-
stitute the bulk of the heterogeneous material:

(1) Very fine-grained quartz-elinossoisite (or epidote) aggregates
with distinctive white porcellaneous aspect in oblique illumination,
and semi-translucent appearance in transmitted light.

(2) Excessively fine-grained semi-opaque particles that are
white, cream, or grey in color and have a polished ceramic-like
appearance in oblique illumination. Quantitatively it can be shown
that these consist chiefly of Si0 2 , AUOa, Ti0 2 , and H,(), and
therefore they are thought to be aggregates of clays and leucoxenic
materials ( rutile or nnatase).

(3) Fragments of saussuritic material or quartz-feldspar-
epidote aggregates; some carbonates may be present. Particles are
usually well rounded, with smooth surfaces and cream to pale
yellowish mottled coloration in oblique illumination.

(4) Aggregates of very fine-grained glaucophanic amphiboles and
epidote; greenish hornblende is sometimes present instead of glau-
eophane.

(5) Deep green, well rounded pumpellyite-plagioclase ag-
gregates; in some instances chlorites are present. Also rounded,
almost spherical grains of deep green color composed solely of ag-
gregated needles of pumpellyite.

(6) Epidote or clinozoisite aggregates that are pale green in
oblique illumination.

(7) Fragments of slightly altered andesite or basaltic rocks,
the individual constituents of which can be readily identified in
the powder obtained by crushing these composite particles in ap-
propriate refractive index liquids.

Corundum

Occasional grains of corundum have been recognized
as rounded, sometimes chipped, anhedra that are color-
less or very pale blue, often with irregular distribution
of color. The frequency with which centered interference
figures were obtained suggests development of basal
parting.

Diamond

Diamond is a mineralogical curiosity in two samples,
and in one of them — sand from a point 220 yards
north of Bolsa Point — constituted 17 percent of the
finest fraction.* Characteristically it takes the form of
highly irregular fragments with most pronounced con-
ehoidal fractures, or as cleavage fragments of triangular
outline. These particles have been referred to as dia-
mond on the basis of the following tests :

(1) The material is quite unaffected by ten minutes immersion
in molten potassium pyrosulfate.

(2) Specific gravities of two fragments were found to be very
close to that of Clerici solution of density 3.5.

(3) Refractive index is approximately equal to that of a
selenium — sulfur glass in which the ratio of Se :S is 3:1.

(4) The fragments are completely isotropic with a distinctive
white glimmer when viewed between crossed nicols ; quite clearly
the glimmer is not weak double refraction since illumination and
darkness were not reproducible for 90° rotations of the stage,
but this illumination could be completely reduced by preventing
any incident light from above from reaching the fragments of
diamond. Presumably then, the excessively high refractive index
and extreme angularity of the mineral permitted much obliquely
incident, yet weak light, to be reflected and refracted into the
axis of the microscope.

Dufrenite

The occasional recognition of soft minerals in beach
sands, such as those of the dufrenite group, was unex-
pected and therefore some pains were taken to check
the identity of the mineral in question.

* This fraction amounted to 0.03 percent of the original sand.

CALIFORNIA DIVISION OF JUNES

[Special Report 59

Tabular, irregularly shaped fragments have a singu-
lar aspecl due to anomalous interference tints and com-
plete absence of extinction, while pronounced preferred
orientation of grains provides more or less centered,
strongly dispersed acute bisectrix figures. The following
optical properties have been determined for material in
sands from near the mouth of Afio Nuevo Creek: a =
1.79-2 ± 0.003, fi = 1.800, y = 1.845, y — a = 0.053,
2V = 35 — 40° ( + ) ; dispersion is very strong with
r > v ; X = bluish green, Y = green, Z = deep brown.
Absorption for Z is barely greater than that for Y,
but is distinctly greater than for X.

These refractive indices are somewhat less than those
determined for carefully verified varieties of the dufre-
nite-rockbridgeite group (Frondel, 1949), or for fronde-
lite and members of the frondelite-rockbridgeite series
(Lindberg, 1949), but higher than those for beraunite, a
dufrenite-like mineral with large optic axial angle and
distinctive pleochroism (Frondel, 1949, pp. 536-539). In
the absence of X-ray powder patterns, however, any at-
tempt to be more specific, other than listing the mineral
as a member of the dufrenite group, is inadvisable.

Garnet

Garnet has been recognized in almost every size frac-
tion of every sample that has been studied carefully,
and three distinct varieties of garnet have been deter-
mined — grossular and hydrogrossular, spessartite-alman-
dine, and very rare uvarovite.

Grossular and Hydrogrossular. Grossular is invari-
ably found in forms ranging from well rounded to con-
choidally bounded fragments, that are either strictly
isotropic or exhibit marked but weak birefringence.
Many fragments are dusted through with fine ferriferous
inclusions that considerably enhance their magnetic sus-
ceptibility, whereas others enclose bands of irregularly
shaped colorless isotropic, unidentified particles of low
refractive index, relative to that of the host. Occasional
grains exhibit features, similar to those produced by
repeated twinning, that may have been caused by defor-
mation.

A refractive index of approximately 1.742 was deter-
mined for a number of fragments but in one determina-
tion fragments with a specific gravity 3.45 gave a low
refractive index value of 1.728; for this material posi-
tive biaxial figures with 2V = 10-15° were obtained.
These data are suggestive of a garnetoid such as hydro-
grossular (Hutton, 1943). Such fragments do not show
evidence of solution but absence of reports of hydro-
grossular in sediments is interesting especially when the
work of Flint and Wells (1941) is taken into considera-
tion. These authors have shown that tricalcium alumi-
nate hexahydrate is unstable in solutions that contain
Na 2 S0 4 when it may be replaced by the "high-sulfate
form" of calcium sulfoaluminate. If, on the other
hand, the aluminate contains some silica as in hydro-
grossular, or Feo0 3 , the stability is enormously increased.
Unfortunately tl e stability of grossular compared with
that of a hydro- a rnet like plazolite was not studied, but
i he lack of occurrences of hydrogrossular as a constitu-
nt of sediments and its rarity otherwise, may be con-
nect* 1 with a decrease in stability of members of the tri-
calcium aluminate hexahydrate-grossular system with

Table !). Physical properties of garnet.

Refractive

Locality

Color

index

Remarks

Small bay, 440 yards

Pale red

1.809

W. of mouth of

Whitehouse Creek

Pale pink with

1.799

Contained inclusions of

paler periph-

gas.

ery

Very palest pink

1.795

Salmon pink

1 .795

Colorless needlelike in-
clusions. R. I. > gar-
net.

Pale brown

center

1.794

I Zoned crystal

Paler brown

periphery

1.797

Very palest pink

1.789

Almost color-

1.790

less

Almost color-

1.792

less

Very pale brown-

1.789

ish pink

Deep red

1.810

Regular skeletal ar-
rangements of rutile
needles.

Brown

1.809

Very pale pink

1.788

Mouth of Gazos

Very pale pink

1 . 794

Sp. Gr.=3.97

Creek

Deep salmon

pink

1.801

Sp. Gr.=4.10

Mouth of Ano Nuevo

Colorless

1.760

Possibly high in gros-

Creek

sular molecule.

Deep pink

1.795-1.800

Colorless

1.770-1.780

2V = 30-40° ( + )
Y -a = 0.003; possibly
close to grossular.

increase in water percentage. Thus a low-silica form of
hydrogarnet in a sediment, or associated with gabbroic
or ultrabasie rocks may perhaps be removed relatively
rapidly in solution, or alternatively converted to the
more stable grossular bv reaction with siliceous material
(Flint and Wells, 1941, pp. 177-8).

In material from the mouth of Ano Nuevo Creek,
rounded fragments with the following rather distinctive
properties were found : refractive indices ranged from
1.770-1.780 with birefringence not in excess of 0.003-
0.004 ; good biaxial interference figures ; 2V = 30-40°
(-{-) ; and in one fragment myriads of transparent color-
less, unidentified needles intersecting at about 60° are
arranged in skeletal fashion. With the small amount of
material available Ca 2+ , Al 3+ , Fe s+ , and Si 4t were found.
The optical and chemical data suggest a member of the
grossular-andradite series, close to the grossular end.

Spessartite-Almandine. Garnet that ranges in color
from nearly colorless through pale pink, and deep
salmon to brown is believed to be spessartite-almandine;
it is found in almost all samples and exhibits a wide
variety of grain shapes. Well rounded or sharply angular
fragments are general, particularly so in fractions of
larger grain-sizes, although there is every gradation be-
tween such forms and eubedra that display dominance
of d {110}, with n {211} less often developed. In the
— 60 -)- 115 fraction of material from the mouth of
Gazos Creek very occasional crystals were, seen with
a {100} dominant, the corners of which are slightly modi-
fied, possibly by development of o {111}, but some degree
of abrasion makes definite recognition of the modifica-
tion uncertain.

1959]

MINERALOGY OF BEACH SANDS

Refractive index and specific gravity determinations
for a number of examples are set out in table 4 with
some additional information. Zoning is frequently devel-
oped but, generally, it was impossible to measure accu-
rately refractive indices of different zones, except in a
case when this property showed insignificant range. In
many instances between the outer border of the homo-
geneous central area and the outer border of the grain
itself, numerous hair-like, concentric zones were seen,
which were made obvious only by distinct differences in
refractive index between adjoining zones.

Vvarovite. Occasional subrounded grains with n =
1.83 and specific gravity = 3.85, found in material from
near the mouth of Pajaro River and elsewhere, have
been identified as uvarovite. Heating had no effect on
these properties (compare gadolinite).

Glauconite

Glauconite is uncommon and its presence in heavy
residues appears to result from admixture with minute
opaque grains, presumably an oxide or hydroxide of
iron, which confers upon the glauconite pellets a specific
gravity that is higher than normal and a greater than
average magnetic susceptibility.

Gold

Gold has been detected with certainty in only the
finest fraction of material from the mouth of Gazos
Creek where it ranks as one of the more plentiful con-
stituents of the mineral assemblage. Nevertheless since
the finest fraction constitutes only 0.56 percent of the
total unfractionated sample, gold is of less importance in
this sand than it would appear to be at first sight.

The metal is found as paper-thin irregular fiakelets
of characteristic color that are soluble in neither con-
centrated HN0 3 nor II CI; a solution of the metal gave
a brownish-red crystalline precipitate with pyridine in
hydrobromic acid.

Leucoxenic Material

Leucoxene, recognized in many sands, does not consti-
tuate more than 3 percent of any size fraction. It occurs
as sub-rounded to rounded pellets that are semi-translu-
cent, buff to white in transmitted light but porcellanous
in oblique illumination ; high refractive index and bire-
fringence are general and a specific gravity of 3.9 ±
0.1 at 20°C. was determined for a few fragments. Inade-
quacy of material prevented determination of actual
composition beyond showing that Ti 4+ appeared to be the
main constituent.

X-ray diffraction powder patterns yielded by three
typical particles correspond exactly in d-spacings and
intensities to those expected for anatase. Furthermore,
the specimens prepared for diffraction consisted of parti-
cles 0.05-0.1 mm in diameter — not powdered material —
and in spite of this, the films exhibited perfect powder
arcs without any trace of spottiness. On the other hand,
no indications of line broadening are evident. Accord-
ingly, the range of diameters of crystallites within each
of the particles mounted for X-ray diffraction must be
approximately 10 ;) to 5 X 10 : ' cm.

These data demonstrate once more that much leucox-
ene is anatase (Tyler and Marsden, 1938; Hutton, 1950;
Broughton et al. 1950).

Magnesite

Colorless rhombohedral cleavage fragments of mag-
nesite were recognized in the — 32 -)-60 fraction of mate-
rial from the mouth of San Gregorio Creek. The parti-
cles, soluble with effervescence in boiling concentrated
hydrochloric acid, have the following refractive indices:
n E — 1.514; n — 1.706; n -- n E — 0.192. These data
indicate a composition close to that of breunnerite.

Monazite

The cerium phosphate, monazite, has been recognized
in many samples as subeuhedral tablets flattened parallel
to a {100}. Fragments of similar habit but sharply
bounded by (001) and (010) cleavage surfaces also
occur, together with occasional basal cleavage fragments
which are easily recognized, owing to low birefringence
and nearly centered acute bisectrix interference figures.
In thin sections of monazite concentrates embedded in
plastic, cleavage planes are much more obvious and in
some instances the (010) cleavage is distinctly better
developed than that parallel to (100) ; the identity of
each of these cleavage directions may be fixed by its
position relative to that of the optic axial plane.

Inclusions are not abundant but give to otherwise clear
grains a dusty aspect when viewed at low magnifications.
The following occluded substances have been observed:

(1) Brown semi-opaque material without definite outline, and
irregularly distributed. This may he penetrative iron-stain since
it is readily removed by acid treatment of more or less finely
crushed crystals.

(2) Aggregates of semi-opaque, isotropic particles of various
shades of dark brown ; these are unidentified.

(3) Colorless acicular crystals with very much lower refrac-
tive indices than those of the host itself. These may be apatite,
since a centrifuged fraction obtained from crushed monazite con-
tained this mineral. A number of these needle-like crystals asso-
ciated with the brown aggregates show some degree of parallelism
In the vertical cleavage.

(4) Brown colored zones at the center of crystals from which
radiate out a few irregular cracks.

(5) Opaque iron oxides that increase the magnetic susceptibility
of the host.

Monazite, from blacksands immediately south of the
mouth of Auo Nuevo Creek and from white beach sands
at Pacific Grove, has been separated in the pure state,
first by screening — since it is largely concentrated in the
finer size fractions — followed by repeated electromag-
netic fractionation, and finally by hand-picking with a
very fine-pointed dissecting needle. Analyses of these
minerals are shown in table 5 along with determinations
of physical data.

The two monazites are similar chemically and optically
and attention may be drawn to the following :

(1) Replacement of Ce 3+ et al. by Th <+ is quite small in each
case and the upset in electrical neutrality is reasonably well bal-
anced by substitution of 1 ,5+ by Si** in tetrahedral coordination.
This is clearly seen in Table 6 where recalculation of analysis no.
2, table 5 on the basis of 10 oxygen atoms to the unit cell is shown.

There is very slight overall departure from the theoretical ratio
for rare earths to P2O5, but, since the sample prepared for analysis
was purified with the greatest care and inclusion-bearing crystals
had been removed, no explanation except inaccuracies in analytical
procedure can be offered now to account for this.

(2) An appreciable amount of copper is present in the Ano
Nuevo mineral, but it is not clear whether this may or may not be
an abnormal feature, since comparative data are unavailable. In
uranoan thorite associated with this particular monazite, however,
analysis shows that 0.11 percent of (JuO is present.

CALIFORNIA DIVISION OP MINES

[Special Report 59

Tabic 5. Analyses and optical properties of monazi

Cp,Os etc 64.8

YaOs see footnote

ThO-> 3.49

Uo0 8 0.25

Fe 2 3 0.11

A1=0 3 nt.dt.

Ti0 2 0.04

MnO nt.dt.

Cu 0.007

Pb 0.018

CaO 0.47

MgO nt.dt.

P 2 5 28.37

Si0 2 0.81

H 2 — 1

H.O + \

0.3G

98.715

tc.
2
63.9
1.1
3.9
0.2
0.2
0.15
0.04
trace
0.09
(CuO)
< 0.01
0.7
0.1
28.5
0.9
0.15
nil(V)

99.84

U 0.21

Th 3.067

Pb 0.018

Age 106 X 10° years *

a 1.787 ± 0.002

7 1.840

y — a 0.053

2V 13° ± 2°

Specific gravity at 22° C 5.21 ± 0.02

Dispersion r < v, distinct

1.788 ± 0.002
1.842
0.054
13° ± 2°
5.21 ± 0.02
r < v, distinct

Monazite from sands, Del Monte Properties, Pacific Grove, Monterey County, Cali-
fornia. In addition, the analyst reports as follows: Zr probably <0.01 percent;
Cb-Ta not detected; yttrium group 0.5-1.0 percent; U3US was determined colorimet-
rically to be 0.25 percent and polarographically 0.24 percent; both Pb and Cu were
determined polarographically. Analyst: Atomic Energy Commission Chemical Labora-
tory Analysis 4453-B.

2. Monazite separated from blacksand paystreaks situated at storm level on beach
immediately south of the mouth of Ano Nuevo Creek. No reaction for Ta or Co
was obtained with tannin. Analyst: C. Osborne Hutton.
•Curtis, Evernden, and Lipson (1958, p. 9), who employed the

potassium-argon method, have determined the ag-es of the Montara

quartz diorite and the Santa Lucia granodiorite to be 91.6 X 10°

and 81.6 X 10" years respectively.

Table 6. Recalculation of analysis of Ano Nuevo Creek monazite.

Ce 2 3

Y0O3 —

ThO,. 3.9

Fe 2 3

ALOa

CaO

MgO

1M ),

Si0 2

Wt.%*

Oxygens

Hfetals

63.9

.5862

3.7081

1.1

.0144

.091

3.9

.0294

.139

0.2

.0036

.022

0.15

.0042

.025

0.7

.0125

.118

0.1

.0023

.023

28.5

1.0035

3.808

0.9

.0300

.142 (

4.12

3.95

* U, Ti, and Cu are omitted since the amounts of each are of lit-
tle significance.

A spectrograph^ analysis of the Pacific Grove ma-
terial made by the Atomic Energy Commission chemical
laboratory is set out in table 7.

Table 7. Spectrographs analysis of Pacific drove monazite.

>10 percent

1-10 percent

0.1-1.0 percent

0.01-0.1 percent

0.001-0.01 percent

<0.001 percent

not detected

Ce, La, P.

Si, Th, Y, Zr.*

Ca, Yb (?).

Al, Mg.

Fe, Pb.

Cu.

Ag, As, B, Ba, Bi, Cd, Co, Cr, Ga,

Ge, In, Mn, Mo, Ni, Pt, Sb, Sn, Ta,

Ti, U, V, W, Zn.

♦The Zr content was estimated but could not be determined

accurately.

Olivine

A small number of anhedral and conchoidally fractured
grains of olivine, free from serpentinization, has been
found in a few samples. The fragments of this mineral
. ■ similar to those of colorless diopsidic augite but were
distinguished therefrom by the lower refractive indices,

higher birefringence, and larger optic axial angle of the
former.

Opaque Constituents *

Non-translucent mineral grains are usually the dom-
inant constituents of the paystreaks and heavy mineral
fractions studied aiul in the majority of sands are most
plentiful in the — 115 +250 size fractions. Particles
range from sharply euhedral to most irregularly or con-
choidally rounded forms. It has been stressed elsewhere
(Hutton, 1950, p. 670) that the difficulties involved in
rapidly and positively identifying opaque or semi-
opaque fragments are considerable, and little progress
has been made in devising new methods or techniques
that might expedite such work. It has been found useful,
however, to separate opaque or semi-translucent ma-
terial into fractions carefully by electromagnetic means.
In general this will segregate magnetite, titanomagne-
tite, ilmenite, chromite, martite, hematite, galena, and so
on, but with some of these recognizable constituents are
others that, although not satisfactorily identified, will be
described in the hope that others may find use for the
data.

In addition to wide field, binocular microscopic meth-
ods, and oblique illumination by white or ultraviolet
light of approximately 2540A and 3660A wavelengths,
the following three techniques were used :

(1) In chromatographic methods, if a small quantity
of undetermined fragmentary material is mixed in
plastic or bakelite and a polished surface prepared, this
surface when placed in close contact with a thin gelatin-
coated layer ** that has been saturated with appropriate
reagents will develop colored areas in those parts of the
gelatin surfaces that immediately adjoin the reacting
mineral surfaces. For instance, the presence of titanium
may be verified in magnetite by pressing a polished sur-
face, as prepared above, against a gelatin surface that
has been saturated with 5 percent solution of chroma-
tropic acid to which some sulfuric or hydrochloric acid
has been added. If titanium is present, a reddish-brown
coloration will develop. The effect of iron may be sup-
pressed by addition of stannous chloride or phosphoric
acid. Alternatively, fine fragments may be scattered care-
fully and evenly on chemically treated gelatin-coated
surfaces backed by paper ; in this case rings or haloes of
reaction are produced surrounding each reacting frag-
ment. The polished surface used for the detection of
titanium may now be used to determine whether vana-
dium is present in the magnetite by placing the polished
surface in contact with a gelatin layer saturated with
tannin and dilute hydrochloric acid; iron may be sup-
pressed with phosphoric acid as before.

This technique follows, in the main, the chromato-
graphic print methods set out by Gutzeit (1942), and
elaborated later by Williams and Nakhla (1951) and can
be successfully employed only with minerals that are not

* Owing to opacity of many minerals except in thinnest splinters,
diagnosis and grain-counting may not always be correct, and the
figures given in the "Opaque grains" column in table 1 may include
chromite, even though a separate figure is quoted for that mineral.
Thus, in making comparisons between sands the reader may prefer
to combine the figures given for "Chromite" and "Opaque grains".
Figures in the "Opaque grains" column exclude both magnetite
and ilmenite.

** The writer has employed gelatin-coated glass and paper, which
may be prepared from standard unexposed photographic negatives
and printing paper by removing silver in sodium thiosulphate and
then washing thoroughly.

1959]

MINERALOGY OP BEACH SANDS

unduly resistant to reaction with the usual attacking
reagents— KCN, NH 4 OH, HC1, HN0 3) H 2 S0 4 , etc. Since
particles in a plastic mount are separated from each
other, there is no electrical conductivity between them
and hence, and unfortunately, electrographic procedures
are not particularly applicable in these cases, unless of
course, large enough fragments are available.

(2) It is of great assistance if one is able to differen-
tiate between grains that are radioactive and those that
are not, or at least to know that specific fragments do
not affect a photographic emulsion after a reasonable
period, say twenty-four hours, has elapsed. For this
purpose particles to be tested are partially embedded
in the softened emulsion of nuclear track plates, Kodak's
types NTA or NTB have been used, the plates set aside
for twenty-four hours, and finally developed, fixed and
washed. If some care is taken in the latter process, the
fragments will be retained in the places into which they
were originally set, so that the plate with fragments
attached may be studied beneath binocular or polarizing
microscope. Following this, any particular fragment may
be removed from the emulsion if additional determina-
tions are to be made with it.

(3) In the fluoride-flux method, if mineral grains are
placed on the surface of a thin cake prepared first by
fusing K 2 C0 3 , NasCO.s and NaF together on a platinum
or nickel crucible lid (Bowie, 1949) and allowed to
solidify, momentary remelting of this cake will allow
incipient reaction between fusion-mixture and mineral
grains. If the latter are uraniferous then the reaction
zones will contain the uranyl ion and will fluoresce with
a bright yellow color in ultraviolet light of either short
or long wavelength. Mineral particles that were shown
by chemical analysis to contain approximately 0.10 per-
cent of UO2 produced reaction zones that fluoresced
brilliantly. It should be noted that this test may be used
for detection of columbium in minerals devoid of
uranium (Mackay, 1951 A, 1951B) but with much care
and some reservation when uranium is also present.*

Magnetite and Ilmenite. With few exceptions, for in-
stance, the sands from near or at the mouths of Ario
Nuevo Creek and Pajaro River, ilmenite is more abun-
dant than magnetite, and in many cases this predomin-
ance is a very striking one (e.g. Gazos and Whitehouse
Creeks). In addition both minerals show marked gran-
ular variation (van Andel, 1950, p. 9 J since, in most
instances, magnetite and ilmenite with grain diameters
ranging from 62-250 microns are more abundant than
any other grain size. Both oxides usually form moder-
ately abraded equidimensional particles with euhedral
and subhedral fragments much less common. Only rarely
has it been possible to identify any of the forms pre-
served on subhedra or partially rounded grains of il-
menite, whereas the octahedral form of magnetite is
often evident. A slight iridescence or polychromatic film
is somewhat more distinctly and more often developed
on ilmenite than it is on magnetite, and this observation
is not strictly comparable with that made earlier by the
present writer (Hutton, 1950, p. 672) for placer mate-
rial, beach and river sands. Magnetite is jet black in
color and in common with members of the spinel group

• In this connection, see particularly comment by Home in Mac-
kay, 1951B, viz. pp. 250-252.

exhibits a shining luster and distinct conchoidal frac-
tures, the concavities and convexities of which tend to
be small. These properties are in contrast to those ex-
hibited by anhedral ilmenite which has a less decided
luster to the black color. Magnetite only occasionally
exhibits films of brown or reddish-brown iron hydrox-
ides, and this might be expected in a situation where
the grains are in a state of constant motion (compare
magnetite in placer material or older river gravels, Hut-
ton, 1950, p. 672).

Quantitative analyses of ilmenite and magnetite have
not been made but the following chemical data have been
determined for a few examples.

(1) Ferromagnetic magnetite which appears to be homogeneous
often contains appreciable Ti 4+ ; this is presumed to be titanomag-
netite.

(2) Black octahedra, or fragments thereof, may show a distinct
range of magnetic susceptibility, and if these crystals are isolated,
crushed in oils, and viewed in transmitted light, the red trans-
luceucy and anisotropic character thereof suggests that the mate-
rial is martite or martitized magnetite.

(.3) Some ilnienites have been observed to produce distinct
fluorescent haloes in short wave ultraviolet light when tested with
Howie's flux, and are apparently uranium-bearing. By comparison
with the effects produced in minerals of known uranium-content,
the ilnienites tested almost certainly contain less than 0.5 percent
of UO». The presence of uranium in ilmenite raises the question
of relationship with davidite (Mawson, 1916, 1944) and a com-
parable mineral from Mozambique (Bannister and Horn, 1950),
both of which contain much higher percentages of uranium, and
are in a metamict state. When it is possible to concentrate a few
milligrams for analysis and X-ray diffraction, this question will
be considered further.

Chromian Spinel. Members of the chromite series of
light to deep brown color are generally present in all
size fractions. In a number of instances they appear to
make up the bulk of opaque and semi-opaque minerals,
but opacity of larger fragments and particles hinders
accurate determination of frequency. If, however, mag-
netite and other ferro-magnetic material are removed
first, the ilmenite-chromite fraction can be concentrated
in a separate fraction when the Frantz separator is set
at a slope of 10° and a tilt of 5°, and a current of
0.25-0.30 amps, is used ; the current will, of course, de-
pend to some extent on the composition of the spinel. If
the material attracted under these circumstances is
viewed with a binocular microscope and oblique illumin-
ation chromite, even if well rounded, may be readily
distinguished from ilmenite on account of the character-
istic jet black color, smooth conchoidal fractures, and
brilliant shining luster. Nevertheless care must be ob-
served in grain-counting since some compositions of
martitized magnetite with similar susceptibilities to
those of some chromites, may be present in the same
magnetic fraction.

On the basis of refractive index determinations alone,
the composition of members of the chromite series ex-
hibit a distinct, yet rather narrow range, and for most
examples 1.970-1.985 was found to be general (e.g. ma-
terial from sands at Bolsa Point). Chromian spinel from
the mouth of Gazos Creek is, however, attracted by a
much weaker field than is chromite from other samples
studied, and a darker brown color is evident. Refractive
indices are decidedly higher, and a range of 2.02-2.04
includes most of the members of the series in Gazos
Creek material ; a few grains are in excess of 2.04 and a
somewhat larger number range down to 1.975.

CALIFORNIA DIVISION OF MINES

[Special Report 59

Pyrite. Pyrite may be recognized in a number of
sands as buck-shot-sized spherules, cubes, dodecahedra,
and subhedral to anhedral fragments. However, visual
recognition is only positive when some indication of
form is present or remains undestroyed in subhedral
fragments. If grains are anhedral or abraded, their
identification may be difficult or uncertain. Color
changes resulting from oxidation may lead to mis-
identification, or minerals such as chalcopyrite, marca-
site, or arsenopyrite may be overlooked. However, none
of these minerals were recognized with certainty, and
even if they were misidentified, they would be fewer
than 1 grain in 300.

When a new screen is employed an appreciable
quantity of brass in thin flakes is removed initially from
the surfaces of the cloth and holders by abrasion ; it ac-
cumulates chiefly in the pan along with the finest
mineral fraction. At first glance this waste has the ap-
pearance of thin fragments of pyrite but may be easily
identified by the relatively smooth, wavy surfaces of the
metal particles, their flexibility, and ready solubility in
dilute HNO3.

Galena. Galena, in sand from Bolsa Point,* consti-
tutes approximately 82 percent of the — 250 fraction.
This is, however, a very small percentage of the total
unfractionated sample since particles with diameters
less than 62 microns make up only 0.03 percent of the
sand. The mineral occurs in a variety of shapes whose
form has been determined principally by perfect cubic
cleavage. In oblique illumination a bright grey color is
evident for most fragments with a thin white film or
surface, possibly cerussite, noticeable here and there.
It is not attracted by strong magnetic fields, and ac-
cordingly is found in the rejected fraction along with
zircon, apatite, rutile, brookite, etc.

Euxenite-Poly erase Series. In blacksand paystreaks
at the mouth of Aiio Nuevo Creek very rare fragments
of a member of the euxenite-polycrase series were de-
tected in the form of nearly opaque, deep brown grains
of marked luster and striking conchoidal fracture. Thin
splinters are brown in color, quite isotropic and, there-
fore, metamict. Refractive index is slightly in excess of
2.05. Following heating at 650° C. in air for one hour,
a distinct rise in refractive index was evident and, al-
though good X-ray diffraction powder patterns were
then obtained with single fragments, anisotropy was not
evident optically. Positive tests for tantalum and nio-
bium resulted from the tannin method (Schoeller, 1937,
p. 89), since, following prior removal of titanium by
tartaric hydrolysis, a tannin complex of orange-red
color was formed.

The positions and intensities of the lines in the X-ray
powder pattern of the heated material, correspond al-
most exactly with those determined by Arnott (1950,
]>. 396) for undoubted euxenite from Nipissing, Canada,
although there are some additional lines in the Ano
Nuevo Creek material. However, these slight divergences
could be due to an inadequate ignition temperature, and
ii addition, might be expected in view of the variability
of cell dimensions of euxenites as reported by Arnott.
In this instance, heating to somewhat lower tempera-

* In this instance, the relative abundance of galena suggests that
its presence may be ilventitious Accordingly, in view of this prob-
ability, it was not 1 ed in table 1.

tnres did not yield a product that gave pyrochlore or
uraninite-type patterns.

The powder pattern of Aiio Nuevo euxenite is com-
pared with that of euxenite from Mattawan Township,
Nipissing District, Ontario, in table 8.

Table S. Poivder patterns of euxenite.

Camera diameter : 114.59 mm.

Radiation : Ni-filtered copper (\ = 1.5418 A).

d meas.

hkl

/4d
\5d

11.6

9.9

7.30

(020)

6.13

5.85

5.16

(110)

3.62

3.66

(130), (111), (040)

3.32

3.36

(121)

2.96

2.98

(131)

2.93

2.76

2.77

(200)

2.61

(141)

2.57

2.58

(002), (220), (150)

2.54

(012)

/2.42
1.2.40

2.43

(022), (201), (060)

3—

2.30

(112), (221), (151)

2.252

(032), (122)

2.193

2.199

(240)

2.178

2.182

(231)

2.106

(132)

2.071

(161)

2.025

(241)

1.961

1.970

(142)

1.926

1.935

(170), (052)

1.886

1.889

(202)

1.817

1.823

(222), (310), (152)
(260), (171), (080)

1.792

1.759

1.769

(062)

1.720

1.723

(311), (330), (261)

1.679

(242)

1.622

1.635

(181), (113), (331)

followed by many additional lines, none of which

exceed

a scale of 4 in Arnott's scheme.

A. Euxenite from the mouth of Alio Nuevo Creek, San Mateo Co,,
California. I am indebted to Professor Adolf Pabst of the Uni-
versity of California for his kindness in providing these X-ray
diffraction data for me.

B. Euxenite, Mattawan twp., Nipissing District, Ontario, Canada
(Arnott, 1950, pp. 396-7, table 5).

d = diffuse line.
B = broad line.

Pumpellyite

In addition to occurrence in composite fragments,
individual rounded particles of aggregates of fine pris-
matic crystals of pumpellyite are found, and for indi-
vidual crystals therein, the following data were deter-
mined in one instance (Aiio Nuevo Creek) :

Elongation

Dispersion

1.685-1.690

70° ( + )

strong with r<v

Pleochroism : strong with

X = Z = pale yellow to colorless
Y = green with a bluish tinge in some
instances.

In sands at the mouth of Gazos Creek, however, pumpel-
lyite with brown tints and uniaxial character was found.

1959]

MINERALOGY OP BEACH SANDS

In oblique illumination pumpellyite is usually bright
green, distinctly brighter in color than the associated
augite.

Pyroxenes

Orthorhombic pyroxenes and clinopyroxenes rank as
the more important mineral groups in most of the sands
investigated, and no sample or size-fraction of any sam-
ple is devoid of at least one variety of pyroxene. Clino-
pyroxenes predominate over rhombic types except rarely
( — 60 -|- 115 fractions of some Princeton sands), and
in approximately 70 percent of individual size fractions
pyroxenes are more plentiful than amphiboles. Notable
exceptions are found in sands from the southernmost
beaches. Amphiboles predominate more frequently in
finer size fractions, possibly because of the ease with
which slender prismatic or needle-like cleavage frag-
ments are developed from larger grains of amphibole by
abrasion, and these pass more readily through finer
screens than the equidimensional pyroxene cleavage
particles.

Augite. Augite ranks as one of the more important
constituents of the sands ; some variety of monoclinic
pyroxene has been found in every sample and in almost
every grade size of these samples. In general, clinopy-
roxenes constitute the greater percentages of the mineral
assemblages of larger grade-size, but notable exceptions
are sands from near the mouth of Butano Creek, where
clinopyroxenes make up more than half of the finest
grade-size fraction.

In most finer fractions augite is anhedral, often show-
ing pronounced conchoidal fractures (fig. 4, no. 20),
although grain shapes determined by prismatic cleav-
ages are common. In addition, such forms are associated
in these size fractions with subhedral and less often
euhedral crystals of simple habit with s {111}, a {100},
m {110}, and b {010} as dominant faces (fig. 4, nos. 21,
23). In larger particle-sizes, irregularly shaped anhedral
fragments are still common, but a considerable degree
of rounding is more often evident.

Results of selective solution may be most pronounced ;
outstanding examples were seen in material from the
beach at Aptos. There were remnants of pyroxene grains
with multiple terminating pyramids in all stages of de-
velopment, the so-called "cockscomb" or "hieksaw"
structures so well described and figured by Ross et al.
(1929, pp. 184-5; plates 23B, C; 24), Edelman and
Doeglas (1932), and others. The etching or solution does
not appear to have preferred clinopyroxenes of any
specific composition nor has it been restricted to frag-
ments of any particular grain-size. On the other hand,
excessively attenuated needle-like fringes appear to be
more or less confined to rhombic pyroxenes (fig. 4, nos.
15, 17) of finer particle sizes.

Clinopyroxenes belong to two varieties, a pale green
diopsidic type and a purple or brownish titaniferous
augite with very weak to moderate absorption. Any
genetic relationship between these two varieties was rec-
ognized rarely, as for example, the occasional fragments
of green diopsidic augite rimmed by titan-augite in ■ — 32
+60 mesh material from the mouth of Tunitas Creek.
In finest size fractions it is usually difficult to detect
any color at all, though color is easily seen in coarser

fragments. Consequently it should be understood that the
figures for green augite in — 250 fractions and to some
extent those for — 115 +250 fractions as well are indica-
tive of clinopyroxenes without reference to color.

Diopsidic augite shows a range from colorless to pale
green with faint pleochroism sometimes evident. Several
determinations of optical properties showed a general
range as follows :

a = 1.690 ± 0.004
Y = 1.715 ± 0.004
Y — a = 0.025
ZAc = 42^4°
2V = 58-62° ( + )

In one case 1.681 was recorded for the X vibration
direction, and in another 1.721 for Z.

Pleochroism is absent in most grains of titan-augite
and is only detectable when purple to brownish tints are
moderately strong. Optical properties generally did not
differ significantly from those recorded for colorless to
pale green diopsidic clinopyroxene, although occasional
fragments from Moss Landing gave: a = 1.705-1.712,
and y = 1.732-1.738. On the other hand, in Aptos ma-
terial a = 1.686 and y — 1-713 were recorded for a
purple augite.

Although diopsidic augite is usually free from inclu-
sions the following have been recognized : plagioclase
(andesine to labradorite), apatite, particles of brown
glass and opaque iron oxides. When separated from the
host, the opaque inclusions from a single grain often
show distinct ranges of magnetic susceptibility and a
■wide range is found in inclusions from grain to grain.
Susceptibility and chemical reactions suggest that the
opaque inclusion material may range from magnetite
through titanomagnetite to ilmenite in composition.
Similar inclusions were recognized in purple-colored ti-
tan-augite and, in addition, inclusions of very delicate
vermicular-like form arranged either irregularly or en
echelon fashion are common. In a few instances the
frequency of iron oxide inclusions in individual detrital
grains, and the proportions of such inclusion-bearing
grains in some sands, are so high that independent iron
oxide fragments cannot be conveniently fractionated
magnetically from the ferromagnesian constituents; the
inclusion-charged ferromagnesian minerals were found
to be as susceptible as many of the iron oxide grains.
This is especially so for sands in the Aptos area where
pyroxenes and amphiboles may predominate over ilmen-
ite for each size fraction separated at 0.15 amps. The
ferromagnetic fractions exhibit similar characteristics
in this case.

Hypcrsthcne. Hypersthene is ubiquitous except in
the finest fraction of sands from the mouth of Tunitas
Creek, and in samples from the southern part of Mon-
terey Bay. Orthopyroxene is usually subordinate to
clinopyroxenes in each size fraction but unlike the latter,
the frequency of the orthorhombic variety is generally
at a maximum between 0.125 -0.25 mm.

The pyroxene occurs in grains that range from highly
irregular anhedral forms with strong conchoidal fracture
surfaces predominant in the finest grade sizes, through
subhedral or well rounded prismatic forms, (fig. 4, no.
1) chiefly in coarser fractions, to distinctly euhedral
crvstals that do not exhibit abrasion effects (fig. 4,

CALIFORNIA DIVISION OP MINES

[Special Report 59

1x2 3

C.O.H.

FIGURE 4. Typical crystals and fragments of pyroxenes. (1) Inclnsion-free, very clear hypersthene with cleavage clearly visible; well
rounded. Oriented perpendicular to X. — 00 +115 fraction of blacksand, mouth of Tunitas ('reek, San Mateo County. X 130. (2) Rounded
green augite. — 60 + 115 fraction of sand from small bay 20 chains west of mouth of Whitehouse Creek, San Mateo County. X 71.
(3) Well-rounded, clear, diopsidic augite; twin lamellae evident. Same locality as no. 2. X 71. (4) Hypersthene. — 115 +250 fraction of
beachsand. Aptos. X 125. (5) Rounded green augite with incipient etching. Same locality and magnification as no. 4. (6) Hypersthene. Same
locality and magnification as no. 4. (7) Same as no. 4. In magnetic fraction separated at — 0.10 + 0.. -> >5 amps. (8) Same as no. 7. (9) Same
as no. 7. (10) Hypersthene with clear remnants at crystal extremities that have the appearance of outgrowths. Fraction, locality, and mag-
nification as for do 7. (11) Pale green augite. — 25 fraction of beachsand from a point north of the mouth of San Gregorio Creek, San
Mateo County. N K). (12) Same as no. 11. (13) Hypersthene. — 115 +250 fraction of Aptos beachsand (magnetic fraction — 0.10 + 0.35
amps). X 125. 5ame as no. 11. (15) Hypersthene. Fraction, locality, and magnification as for no. 11. (16) Same as no. 11. (17) Same

is no. 15. (18) (ilomeroporphyritic aggregate of hypersthene crystals. — 32 +60 fraction of Aptos beachsand. X 54. (19) Same as no. 11.
20) Titan-augite, much chipped. Fraction, locality, and magnification as for no. 2. (21) Green augite oriented parallel to (010). Fraction,
icality, and magnification as for no. 13. (22) Clear, slender hypersthene crystal in heavy residue from I'urisima formation. North of mouth

of San Gregorio Creek, San Mateo County. X lcSO. (23) Same as no. 21.

1959]

MINERALOGY OF BEACH SANDS

110s. 10, 22) ; the cuhedral ones are perhaps more usual
in finer size fractions but are also found among' the
coarser sizes. Occasional undamaged glomeroporphyritic
aggregates have been found (fig. 4, no. 18) in which
the individuals show no simple crystallographic relation-
ship to one another ; twinning is thus discounted.

As with augite, hypersthene exhibits every degree of
completeness of solution effects from incipient develop-
ment of multiple pyramidal terminations (fig. 4, nos.
6-9) to minute fragments with very slender, needle-like
attenuations that are often two or three times as long
as the central remnants (fig. 4, nos. 15, 17). It should be
noted at this point that fragments with the most pro-
nounced solution effects, that is, remnants with the long-
est and most delicate pyramidal terminations, are more
or less restricted in their distribution to the finest grade
size ; in other words, to grains with diameters not in
excess of 62 microns. Larger pyroxene fragments (125-
250 microns) exhibiting solution effects show some de-
gree of blunting of the multipyramidal terminations,
and extremely attentuated needle-like fringes are ap-
parently unable to develop or to be maintained in such
instances (fig. 4, nos. 8-9). This would appear to be a fine
example of the incompetence of abrasion processes, even
on open beaches exposed to storm conditions of some
violence, when minute particles are cushioned by water
films.

In the samples investigated the minute fragments
with attenuated fringes did not appear to be limited to
any particular zone of a beach and do not seem to be
any more numerous at storm level than at low water
mark.

The finest sized particles of hypersthene are colorless
or nearly so, but coarser material is moderately pleo-
chroic according to the usual scheme. Distinct dif-
ferences in absorption between the three vibration
directions are difficult to detect but where absorption
is most pronounced the scheme X > Z J> Y would seem
to apply. In some preparations hypersthene fragments
were found to be oriented in the mounting medium with
the basal plane parallel to the plane of the microscope
stage, and at first sight the pleochroism, brown (X) to
golden yellow (Y), suggested that of staurolite. However,
such grains were perpendicular to the bisectrix Z and
have other properties characteristic of hypersthene.

Except for specimens from occurrences near Pajaro
River, refractive indices fell within the following range
in the majority of samples :
a = 1.685 — 1.688
y = 1.698 — 1.700
7 — = 0.012 — 0.013

Zoning may be quite marked and is made more apparent
by distinctly stronger absorption in narrow peripheral
zones that are not necessarily abruptly demarcated from
the central areas.

In material collected just above high water level,
three-quarters of a mile south of the mouth of Pajaro
River, the following values were obtained :

a= — , 1.694, 1.696, 1.696

Y = 1.699, 1.708, 1.710, 1.710

Taken together, the refractive indices indicate a com-
positional range of 33-42 percent of the orthoferrosilite
molecule (Henry, 1935, p. 223, fig. 1).

Very few hypersthene fragments are completely de-
void of inclusions, and the following are common :

(1) Rounded or irregula rly shaped grains of magnetite, titano-
magnetite and ilmenite ; on account of the abundance of these
contaminants in some cases, pyroxene crystals may lie ferro-
magnetic or so strongly paramagnetic that they are concentrated
with ilmcnite when the sands are magnetically fractionated.

(2) Unidentified disoriented, colorless grains of low refractive
index.

(3) Irregularly shaped and spaced gas cavities; occasionally
these may be grouped into dense aggregates.

(4) Prismatic crystals of apatite.
(."-)) Glass.

Mi) Euhedral zircon.

(7) Most, or combinations, of the minerals or phases just listed
may be found aggregated into distinct zones that exhibit marked
parallelism to orthopyroxene crystal boundaries.

Rutile

Rutile, a constant minor constituent, does not exceed
1 percent of any fraction of any of the sands studied.
Worn and broken prismatic crystals with rare geniculate
twins are characteristic and these exhibit either (a)
golden yellow to red-brown dichroism with intense ab-
sorption parallel to the c axis in a few cases, or (b)
golden yellow to yellowish-brown for the ordinary and
extraordinary rays respectively, with little difference in
absorption in the two directions. In the — 60 -f- 115 size
fraction, Whitehouse Creek material contains fragments
that are very deep red in color and almost opaque for
any orientation. A score of fragments were hand-picked
and after fusion in potassium pyrosulfate and solution
positive tests for tantalum were obtained; the presence
of niobium was not verified.

In oblique illumination rutile may be readily identi-
fied and differentiated from oxyhornblende, cassiterite
and other dark brown prismatic minerals by its adaman-
tine luster; the presence of striations is an assistance.

When color is intense rutile fragments are nearly
black in oblique lighting but are, however, rarely devoid
of a dark brown resinous glint ; the latter is particularly
evident where conchoidal fractures have partially devel-
oped without actual separation of splinters.

Sphene

Sphene is ubiquitous and, in general, crystals and
fragments that have diameters ranging from 125-250
microns are noticeably the more abundant. Habit varies
considerably from grain to grain but the range of forms
does not change appreciably from sample to sample.
Every gradation is to be found from sharply euhedral
"envelope "-shaped crystals with dome {102}, basal
plane {001}, and orthopinacoid {100} prominently de-
veloped, to fragments of euhedra, or on the other hand,
well rounded particles that may exhibit chatter marks.
In crystals from the south side of the mouth of Tunitas
Creek, deep rhomboidally shaped pits were seen, and at
the same time pronounced zoning was made evident
solely by patchy distribution of anomalous interference
tints in orientations with Bxa perpendicular, or nearly
so, to the microscope stage.

Two varities of sphene have been noted and both of
these are usually present in the same sample. The first
of these forms pale yellow, well worn grains with a
dusty appearance that may be due to numerous unidenti-
fied translucent, pale yellow to colorless inclusions. Nu-
merous cracks are present that do not seem to originate

CALIFORNIA DIVISION OF MINES

[Special Report 59

at any specific point or inclusion. Due to the degree of
rounding, preferred orientation of crystals in mounting
media is not very noticeable. Dispersion is distinct and
pleoehroism faint yet clear, with X' = pale yellow to
nearly colorless and Z' = deep salmon pink (rarely red-
brown ; Whitehouse Creek), in some instances, but with
X' = pale golden yellow and Z' = golden yellow domi-
nant. Pleoehroism may be much more satisfactorily ob-
served when crystals, or fragments thereof, are immersed
in a liquid of refractive index about 1.95, since, in
mounting media of very dissimilar refractive index, ap-
propriately oriented crystals exhibit marked change of
brightness on rotation of the microscope stage due to
high birefringence ; this effect of alternate brightening
(X' parallel to plane of polarized light) and darkening
(Z' parallel to plane of polarized light) is suggestive of
pleoehroism.

The second variety of sphene is also pale yellow,
although in some instances nearly colorless, and crystals
and fragments are generally free from inclusions. Round-
ing is less noticeable and angular, or often euhedral
forms with {102} prominent, are more common. Pre-
ferred orientation of grains in mounting media is much
more obvious than is the case with the first variety,
interference figures are clearer, dispersive effects are
more striking both in interference figures and between
crossed nicols, and the optic axial angle is greater.
Cracks are not so evident.

No significant differences in the a refractive indices
have been detected so far, and values that range from
1.887 to 1.898 have been found for the two varieties. Ad-
ditional work in this connection is necessary.

Tantalite

Identification of rare, dark red, irregular fragments
in material from the mouth of A no Nuevo Creek as
tantalite is somewhat doubtful, but the data determined
are recorded for the sake of completeness and to point
out that distinction between tantalite and deeply colored
tantalian cassiterite, on the basis of some optical prop-
erties alone, may not be entirely satisfactory unless com-
plete information can be obtained. The refractive index
for X' is in excess of 2.06 (distinction from cassiterite)
but birefringence does not appear noticeably different
from that for cassiterite. Fragments are unaffected by
hot concentrated HC1, give a negative test for Sn 4+ with
zinc and HC1, and curiously, if tantalite is a correct
diagnosis, contain negligible Mn 2+ ; with tannin, orange
colored complexes of Ta 5+ and/or Nb r,+ compounds were
obtained. Cleavage is not apparent, nor could satisfac-
tory interference figures be secured.

Uranoan Thorite

Uranium -bearing thorite, a constituent of many sands
collected at points between Princeton and Monterey Bay,
is largely restricted in size to diameters less than 125
microns.

Habit and Color. Most thorite forms exceptionally
well abraded particles, occasionally spherical, with traces
of conchoidally shaped fracture surfaces that are very
nearly obliterated by the natural polishing processes to
which the mineral has been subjected. There is every
gradation between such forms and less common stumpy,
prism-like, grains from which all traces of crystal faces

have been removed, and, in the other extreme, highly
angular fragments with strikingly well developed con-
choidal fractures. No grains were found with definitely
identifiable crystal faces.

A rather wide range of color is found and an opal-
escent pale green, close to Ridgway's Light Grape Green
(25'" YG-Y, b) is possibly the dominant one. A shade
of brown is less often evident whereas some crystal frag-
ments trend towards Ridgwav's Corydalis Green (29'"
GG-Y, d). A color- close to Courge Green (25 YC-Y, i)
is found for a few grains with Orange-Citrine (19 YO-
Y, k) unusual. Almost colorless particles are rare. The
color of a pure sample of uranoan thorite particles with
diameters 62-125 microns is comparable to Ridgway 's
Yew Green (27" G-Y, m) when viewed en masse in ordi-
nary light.

The prime cause of the wide range of colors found in
Aiio Nuevo Creek thorite is obscure. The green opalescent
color that is most commonly seen may result from the
presence of U 4+ ions, and perhaps much paler yellowish
green tints might arise when U 0+ ions are dominant
instead. On the other hand, the range of colors displayed
by this mineral is rather strikingly similar to that found
in common silicate glasses with comparable or less
amounts of iron to that found in this mineral (table 9),
that have been prepared under a variety of oxidizing
and/or reducing conditions. The range of color that may
be developed in such cases is clearly due to the small
percentage of iron present, but little appears to be
known of the relationship between the valence of iron
and the color of the corresponding glass. Certainly, it
is not merely a question of divalent iron producing a
green glass, and a brown glass resulting from oxidation
of iron to the trivalent state, since in some instances,
green "lasses have resulted with iron in the higher state
of oxidation ; even blue colors have developed in glasses
when approximately equal amounts of Fe 2+ and Fe 3+ are
present. That thorite, described here, is in a glassy,
metamict condition, does not make the comparison with
artificial silicate "lasses any more valid, since a wide
range of color from green to brown may be observed in
non-metamict thorite.

Thus little specific data are available to assist in re-
solving this question of color, but it is tentatively sug-
gested that the range of color in thorite may be due to
the iron present, rather than to the uranium content.
The range of magnetic susceptibility found for this
mineral may support this conclusion.

In oblique illumination uranoan thorite is readily dif-
ferentiated from other pale green or brownish green
grains, such as many composite fragments of saussuritic
composition, grossular, members of the clinozoisite-
epidote series, vesuvianite, etc., first, by striking opal-
escent or chatoyant appearance, and second, by remark-
ably smooth and polished surfaces of the rounded
particles. Here and there, for example at the mouth of
Gazos Creek, thorite may exhibit curious breadcrust-
like surfaces that are particularly evident in brown-
colored varieties but not restricted thereto.

In shortwave ultraviolet light (2540 A.) a very faint
deep blue fluorescence was detected for some particles,
but when these were segregated by hand-picking and
examined in liquid media by transmitted light, nothing
distinctive was detected. On the other hand, a blue

1959]

MINERALOGY OF BEACH SANDS

fluorescence of brighter hue was noticed for patches of
alteration ( ?) material associated with some thorite,
and, here and there, bright yellow-green fluorescent
spots suggest the presence of uranyl compounds as other
alteration products. No effects were noted when ultra-
violet light of longer wavelength (about 3600 A) was
employed as the source of oblique illumination.

The ability of uranoan thorite described herein to
produce faint fluorescence in shortwave ultraviolet light
appears to be' destroyed by heating to temperatures in
excess of 680°C.

Inclusions. Inclusions are uncommon, and especially
so for highly translucent clear green varieties ; on the
other hand, alteration products appear to be slightly
more frequent in brownish grains than in green. Some
of the inclusions and heterogeneities observed may be
summed up as follows :

(1) Brown areas that appear due to clouds of "limonitie" dust-
like particles in grains that otherwise exhibit blotchy areas of weal;
birefringence.

(2) Zonary arrangement in which relatively wide brown central
areas of dusty aspect are sharply demarcated from clear, green
peripheral zones.

(3) Yellow to orange colored blotches, often anisotropic, in
otherwise homogeneous, inclusion-free crystals of pale green color.
The yellow or orange material is soluble in warm dilute HNOa,
and since this solution fluoresces in shortwave ultraviolet light, the
presence of the uranyl radical in these distinctively colored areas
is suspected.

(4) Aggregates of unidentified dust-like particles from which
systems of cracks may radiate outward.

(5) Semi-opaque isotropic areas of much lower refractive index
than the thorite.

(6) Sharply demarcated, unsymmetrieal narrow zones of color
banding, (fig. 5, no. 9.)

(7) Cavities filled with gas or liquid; rarely bubbles (fig 5,
no. 19).

(8) Systems of anastomosing cracks, usually thread-like, that
do not seem to be associated with inclusions of any kind.

(0) Deep brown opaque inclusions; usually as rounded grains
or blebs.

When free from inclusions or from what seem to be
alteration products, uranoan thorite is generally iso-
tropic, though a few grains have a faint glimmer of bire-
fringence. A spherulitic structure on a eryptocrystalline
scale is suggested for the birefringent grains on account
of the appearance of minute black crosses when such
material is viewed between crossed nicols; the arms of
the crosses are parallel to the ocular cross hairs and the
direction parallel to the elongation of the "fibers" is
fast.

Chemical Properties. Uranoan thorite is exceedingly
refractory and even when reduced to excessively fine
powder, hot concentrated acids have little effect thereon,
and gelatinization was not evident. However, if frag-
ments of thorite are boiled in a strong solution of oxalic
acid for about 2 minutes, washed, and then dried, white
films of thorium oxalate are developed; this behavior
facilitates recognition of thorite when other green, iso-
tropic, but non-thorium-bearing minerals are present.
A sample was prepared by careful electromagnetic frac-
tionation, after preliminary concentration by screening
and flotation, and brought to a state of high purity by
careful hand-picking in oblique illumination Avith white
light and finally with shortwave ultraviolet light. The
latter precaution was necessary in order to guarantee
absence of both zircon and scheelite; neither ZrO^. nor
W0 3 were detected by analysis.

The composition of thorite from A no Nucvo Creek
is quite similar to that recorded by George (1951, p.
131) for thorite from concentrates obtained by the
La Grange Dredging Company in the course of opera-
tions on the Tuolumne River, near La Grange, Cali-
fornia. However, uranoan thorite from the Aho Nuevo
locality contains an appreciable amount of copper
and the total quantity of water is released at tempera-
tures below 105° C. The. analysis of Tuolumne River
thorite, on the other hand, shows moderate amounts
of alumina and water, although George does not give
any indication of the temperature at which water was
given off; in fact, the considerable quantity of water
in thorite from the Tuolumne River locality is not com-
mented upon by George, other than to state that the
high specific gravity "is probably attributable to the
absence of appreciable water of hydration."

Table 9. Analyses of uranoan thorite.

A. B.

Rare earths 0.24 0.54

Th0 2 72.93 71.61

U0 2 6.95 8.36

FeO 0.58 0.59

A1 2 3 0.32 1.29

TiOo 0.04 0.10

MnO <0.01

CuO _' 0.11

PbO 0.1O 0.10

CaO — 0.42

MgO 0.07 0.01

PjO= trace

Sif) 2 17.96 16.47

H,0 + nil , rteP

H,0— 0.22 p HO

99.94 100.00

A. Uranoan thorite separated from blacksands, mouth of Aiio Nuevo
Creek, San Mateo County, California. TasOn, NbsOo, Zr0 2 , and
WO.i were not detected. Rare earths are chiefly Y 2 Os. Analyst :
Johnson, Matthey.

B. Uranoan thorite from dredge concentrates, La Grange, Califor-
nia. Total includes Zv0 2 0.07 per cent (George, 1951, p. 131,
column 3.). Analyst: National Bureau of Standards

When the two thorite analyses are calculated on the
basis of molecular proportions the ratio of ThO a and
other metal oxides to silica is low in each case, when it
should be 1:1. For the Ano Nuevo mineral Th0 2 etc.:
SiC\> is 1:0.903, whereas the corresponding ratio for
thorite from Tuolumne River (George, 1951, p. 131)
is 1:0.845, a discrepancy which George believed might
be due to an incorrect silica determination. Although
this could be the ease, it should be remembered that we
are unaware of the states of oxidation of both iron and
uranium. Certainly in view of the low percentages of
Fe- + an incorrect assumption in this respect will be of
little moment but with uranium it is a different matter.

Frondel (1953) has demonstrated that [Si0 4 ] groups
in thorite may be replaced by [OII] 4 in a manner sim-
ilar to that found in hydrogrossular and other minerals.
If, then, the two analyses in table 9 are recalculated on
the basis of 16 oxygen atoms to the unit cell, and water
is taken into consideration (table 10), much better ratios
between Th etc. and (Si+H) are obtained (1:0.98 and
1.08 for A no Nuevo Creek and Tuolumne River thorite
respectively). This seems to support the conclusion that
the water determined to be present in these two minerals
may instead, be [Oil] 4 substituting for [Si0 4 ], rather
than water molecules, although it should be stressed
that the 0.22 per cent of ILO in Aho Nuevo Creek

CALIFORNIA DIVISION OF MINES

[Special Report 59

FIGURE 5. Typical habit and form of detrital uranoan thorite. Locality, beachsands at
the mouth of Alio Nuevo Creek. Magnification, X '100. (1) Slightly abraded, green thorite
of tetragonal form. (2) and (3) Abraded and chipped, green anhedra. (4) Excessively
chipped and rounded grain; color pale green. (5) and (6) Chipped, abraded grains; pale
green. (7) Poorly birefringent, orange-colored thorite. (8) Isotropic orange thorite. (9)
Abraded brown thorite with bands of inclusions of dust-like size, but undiagnosed. (10)
Abraded chip of dirty green thorite. (11) Well-rounded clear green thorite. (12) Pale
green thorite with semi-opaque inclusions; striations may be zonary structure. (13) Deep
green abraded grain with lines of submicroscopic inclusions. (14) Green fragments, per-
haps a basal section. (15) Deep green particle of thorite. (16) Practically colorless thorite
with chatter marks. (17) and (18) Clear brown grains. (19) Clear green particle with gas

cavities.

19591

MINERALOGY OF BEACH SANDS

Table lo. Recalculation of thorite analyses on the

basis of Id oxygen atoms per unit-cell.

Table 11. Effect of heating on physical
properties of Ai'io Xitcro thorite.

Ano Nuevo Creek

Tuolumne River, (La Grange)

Weight
percent

Metal
atoms

Weight
percent

Metal
atoms

R.E.*

TI1O2

UO2

FeO

AI2O3

Ti0 2

CuO

CaO

MgO

S1O2

H2O

0.24
72.93
6.95
0.58
0.32
0.04
0.11
0.42
0.07
17.96
0.22

.03'
3.54
.33
.10
.08

.01
.09
.02,
3.84/
.31/

4.20
4.15

R.E.*

TI1O2

UO2
FeO

AI2O3

TiOa
CuO
CaO

MgO

Si0 2
rhO

0.54
71.61
8.30
0.59
1.29
0.10

0.01

16.47

0.86

.06
3.45
.39
.10
.32
.01

3.49\

1 .2l/

4.33
4.70

Formulae :

A. [Th3..i4 U0.33 Yo. 03 Feo.10 Alo.os Cuo.m Caoiw Mgo.02] [SiC>4]3.s4[ (OH)4]o.3i

B. [Th3.45U0.39 Y0.00 Feo.io Alo.su Tio.01] [SiCk]s.«>[ (OH)<]i.a

* R.E. refers to rare earth.s and in both instances these have been
taken to be yttrium.

thorite was given off below 105° C. The ratio of 1:1.08
in Tnolnnme River thorite is, of course, too high, and
some water molecules may be present as well in this case.
Although the work of Frondel has shown that altera-
tion of primary thorite to hydrothorite gives rise to a
product that is fully crystalline, and not metamict, the
minerals described here are metamict.

Physical Properties. The mineral is either isotropic,
or at the most, it may exhibit feeble birefringence ; ac-
cordingly, it is in a metamict condition. In no instance,
however, were values comparable to those recorded by
George (1951) for La Grange, Tuolumne River thorite
observed, nor has the present writer ever found bire-
fringences of the order noted by George in his own con-
centrates of Tuolumne River thorite. A range of re-
fractive indices has- been determined for the analyzed
material, and 1.850±0.002 appears to be inclusive. For
impure thorite concentrates, a range of 1.841-1.859 was
found, but with the greater proportion of the material
lying within the range 1.849-1.854. Both refractive in-
dices and color undergo marked transformations when
Ano Nuevo thorite is heated in air, and the data in
table 11 are indicative of these changes.

Since heavy media could not be profitably employed
for specific gravity determinations, a micropyenometric
method was used ; this entailed use of several milligram
amounts of thorite grains, rather than individual par-
ticles, and the values obtained in this manner for sev-
eral pure fractions that exhibited slightly differing
magnetic susceptibility were 6.27±0.03 at 26° C.

Employing a camera of 57.3 mm. diameter, and nickel-
filtered copper-radiation, a faint, but well-defined pow-
der pattern was obtained from a single crystal of uranoan
thorite, 0.125 mm. in length, after it had been heated
in air for 4 hours * at a temperature of 860° C. The
lines on this pattern are those yielded by the face-cen-
tered cubic lattice of thorianite (table 12). After de-
mounting' the crystal, it was heated again, but this time
to a temperature of 1250° C. for an additional four-
hour * period, and the X-ray diffraction pattern now

* It was determined in subsequent experiments that much shorter
periods of heat-treatment would cause satisfactory recrystalliza-
tion of metamict thorite.

Refractive indices

Temperature
in degrees Centigrade

Major
portion

Range

Color in transmitted light

Normal

680° for 2V 2 hours

800° for 3J4 hours-

860° for 4 hours. ..

1.850
1.865
1 . 838
1.805
1.788

1.841-1.859
1.858-1.869
1.829-1.842
1.799-1.808
1.779-1.791

Pale green
Golden brown
Golden brown

1100° for 4 hours

Very dark brown, (dark
coffee brown in oblique
illumination).

Table 12. Poieder pattern of uranoan thorite after being heated

to 860° C. for four hours. Locality: Mouth of Ano Nuevo Creek,

San Mateo County, California.

dot, hkl I*

3.23 (111) 10

2.78 (200) 6

1.96 (220) 7

1.69 (311) 8

1.62 (222) 2

1.40 (400) 2

1.29 (331) 4

1.26 (420) 3

1.15 (422) 3

108 ((511)1

1.08 J (333) I

0.09 (440) v. faint

0.95 (531) 2

04 f (600) ] „

U.J4 ^ (442) ^ 2

0.S85 (620) 1

* Intensities were determined visually.

obtained from the crystal corresponds to that of the
monoclinic dimorph of Th,Si0 4 — huttonite.

Age of Ano Nuevo Creek Thorite. While fully cog-
nizant of the uncertainties attached to age determina-
tions of material that has not been found in place, it is
interesting that the ratio U-Th/Pb for Ano Nuevo Creek
thorite leads to an age of 25.25 x 10° years when Holmes'
(1931, p. 207) logarithmic formula is employed, and that
this is close to the age of 21 x 10° found by George
(1951, p. 130) for Tuolumne River thorite of placer
origin that was apparently derived from Sierra Nevada
intrusives.

Although the original host of the Ano Nuevo Creek
thorite is not known, it would seem most probable that
it has been derived from Sierra Nevada intrusives. Ac-
cordingly, an age of 25.25 x 10 r ' years is quite unlikely,
and in view of the well-known solubility of the thorium-
lead isotope, Pb 208 , a loss of lead may have taken place
during the process of metamictization, or perhaps dur-
ing the transfer to its present locality — especially if
acidic ground-waters were available.

Topaz

Topaz was recognized in the finest size fractions of two
samples as water-clear, but irregularly shaped cleavage
fragments that exhibit centered biaxial interference
figures.

Tourmaline

Tourmaline, surprisingly rare hut widely distributed,
usually forms abraded or fragmentary short to stumpy
prismatic crystals with terminal faces that are occasion-
ally preserved. Clouds of dust-like particles are often

CALIFORNIA DIVISION OP MINES

[Special Report 59

present and parti-colored fragments were rarely seen.
Crystal fragments with quite intense dichroism in
shades of brown appear to be dominant, with blue or
purplish tints much less abundant, Other dichroic
schemes infrequently observed are == red, E = color-
less (Aiio Nuevo) ; O = deep green and nearly opaque,
E = pale green (Bolsa Point); = deep greenish
brown, E = red-brown (Butano Creek).

Vesuvianite

Rare vesuvianite forms rounded to sub-rounded color-
less to very pale green grains of faint birefringence, but
material from sands at the mouth of Whitehouse Creek
was rather distinctive ; the following data were deter-
mined for it :

1. The mineral was concentrated electromagnetically when the
separator was set with a slope of 15°, a tilt of 5°, and a current
of 0.45 amps, was employed.

2. a = 1.710 ± 0.002
T = 1.719

7 — a = 0.003

o. The optic axial angle was zero in red light, but a small angle
is evident in light near the short end of the visible spectrum ;
sign is positive.

These data are comparable to those given by Winchell
(1951, p. 508) for the variety, viluite, but since insuffi-
cient material is available for any additional work fur-
ther comparison is unwarranted at this time.

Xenotime

The yttrium phosphate xenotime has been definitely
recognized in one heavy mineral assemblage, the — 115
-f250 mesh fraction of material from the mouth of
Aho Nuevo Creek. It was found concentrated in the
electromagnetically separated monazite-rich fraction, al-
though xenotime was found to have a greater suscepti-
bility than that of monazite.

Xenotime forms colorless, rounded, equidimensional
grains of dusty aspect due to fine pale colored inclus-
ions which are often aggregated together to produce
what at first sight has the appearance of a stain.

It is uniaxial and optically positive with a = 1.724
and y = 1.818. Tests with alpha-track plates suggest
that the xenotime described herein is distinctly more
radioactive than the associated monazite but otherwise
no compositional data are available.

Zircon

Zircon is a constituent of each of the size fractions
—250, —115 +250, and —60 + 115 in every sample
studied. In the first size group zircon may range from
75 percent down to approximately 1 percent, but with
higher values the more usual ones. Zircon exhibits very
much the same range of frequency in the second size
fraction, but in the — 60 -j- 115 and coarser grade sizes
zircon percentages decrease rapidly.

It is found in a wide variety of forms and, except for
the more obvious division into colorless and purplish
types, no simple classification appears to be possible.

Colorless Zircon. By far the greater proportion of
zircon in the finest size fractions is euhedral but the de-
gree of rounding increases strikingly with increase of
/rain-size and may attain considerable perfection with
the development in some instances of cigar-shaped
forms. Crystals less than 62 microns in diameter show
little evidence of abrasion whereas the larger crystals or
fragments in the — 115 -f 250 fraction do. Fragments

bounded by conchoidal fractures are found in the finest
fractions but they are increasingly less frequent in as-
semblages of larger grain size. In more rounded grains
pits and chatter-marks are often seen by inspection in
oblique illumination.

The dimensions, that is length and breadth, of euhedra
show a fairly wide range but no distinct groupings seem
feasible. The ratio length: breadth ranges from 1.9-4.5
with the majority of grains from all samples, 2.2-2.5.

Crystals of moderately complex habit are dominant
whereas crystals with first order prisms and pyramids
alone are decidedly rare. Perhaps the most common
forms developed in any one crystal are m {110}, a {100},
x {311}, p {111}, and u {331}.

Inclusions are general, and although few grains are de-
void of them, only rarely is a considerable amount of the
zircon of any one sample moderately paramagnetic on
account of aggregates of opaque iron oxides ( — 115 -4-
250 fraction of material from near the mouth of White-
house Creek). The common forms of inclusions observed
are :

(a) T'noriented needles of dark brown material (=rutile V).

(b) Narrow thread-like channels parallel to the c-axis that may
be gas-filled since the refractive index is extremely low.

(d) (Jaseous and liquid cavities.

(e) Colorless, acicular crystals as yet unidentified.

(f) Prisms of rutile, apatite, zircon, monazite.

Occasional zircons of faint blush pink color were
noticed and such crystals are probably more correctly in-
eluded with the group just described than with hyacinth,
since they do not exhibit any of the characteristic
features seen in hyacinth. Such zircons are generally
sharply euhedral and perhaps more often free from in-
clusions than colorless zircon ; otherwise they are similar.

Hyacinth. The purple-colored variety of zircon, hya-
cinth, is present in most assemblages but it rarely ex-
ceeds more than a few grains in any one sample.
Although restricted numbers did not permit detailed
studies, the characteristic features of color, zonary struc-
ture, notable rounding, anastomosing systems of fissures
or cracks are all present, and comparable in every Avay
to those previouslv recorded for hyacinth (Tyler et al.,
1940; Ilutton, 1950).

Malacon. In material from near the mouth of Tunitas
Creek, San Mateo County, rare particles were observed
that are believed to be malacon, but this opinion is put
forward with some uncertainty. The dusty, brown,
grains have tetragonal symmetry, and a birefringence
that does not exceed 0.015. Refractive index and specific
gravity are approximately 1.78 and 4.1 respectively.

Doubtful Identifications

In the foregoing mineralogical descriptions attention
has been drawn to the uncertainty of some data and the
interpretations based thereon. Furthermore in some in-
stances optical data determined for some minerals may
not correspond with any recorded data, or correspond in
a general way only with some extremely rare or unusual
species so that reference to such mineral types does not
seem to be warranted. In every case where there was
some doubt insufficient material prevented application of
adequate chemical or optical tests. However, the incom-
plete data are recorded in the hope that they may prove
of use to other investigators.

1059]

MINERALOGY OF BEACH SANDS

In a fraction rejected by the electromagnet at maxi-
mum field strength occasional grains were recognized in
material from the mouth of Alio Nuevo Creek ( — 115 -\-
250 mesh), with the following properties:

Color : deep blue to bluish green.

Pleochroism : faint.

N : 2.0 (Cfl).

Birefringence: 0.03 (ca).

Uniaxial and optically negative.

These data are comparable to those recorded for the
hydrous oxychlorides boleite and pseudoboleite.

From sands near the mouth of Whitehouse Creek oc-
casional fragments were found in a magnetic fraction
rejected at 0.75 amps but attracted at 1.18 amps, (slope
15°, tilt 5°), that have not been satisfactorily identified.
Significant properties recorded for this mineral are :
Colorless; one good cleavage; a = 1.685 ± 0.002;

Y = 1.695; y — a = 0.010; 2V = 35 — 40° ( + ).

These data suggest zoisite but dispersion is absent and
that mineral has somewhat higher refractive indices;
furthermore zoisite is attracted by much weaker field
strengths than used here.

In the — 60-(-115 fraction of material from the
mouth of Gazos Creek rare fragments were noted with
the following properties :

Colorless, rounded fragments; a = 1.731 ± 0.002;

Y = 1.752; Y — a = 0.021; 2V = 65° (— ) ; r > v,
very strong. No chemical data are available.

PROVENANCE

Although detailed studies have not reached a state of
completeness that would permit an adequate report con-
cerning provenance, it may be stated that all of the
minerals recognized in the beachsands with the excep-
tion of cassiterite, chrysoberyl, corundum, diamond,
dufrenite, euxenite, scheelite, tantalite, thorite, ve-
suvianite, and xenotime have been found in assemblages
of heavy mineral fractions prepared from Cretaceous
and Tertiary sandstones, siltstones, volcanic ash beds,
etc., in this area. Undoubtedly these must have pro-
vided much of the detritus that is now differentially
sorted and concentrated on the present day beaches.

Study of heavy fractions prepared from soft brown
sandstones of the Merced formation : (Lawson, 1914)
proved instructive and pointed to a source for at least
some of the deeply etched pyroxenes previously de-
scribed, since both orthorhombic and monoclinic forms
are very well represented in — 60 + 115 an d — H5 size
fractions of the large residues. 2

The mineral frequencies, based on averaged counts of
300 grains in each of three samples of Merced sand-
stones, are set out in table 13. The dominance of green
hornblende is noteworthy, particularly since this is
characteristic of beach sands concentrated at the north
end of Half moon Bay (see Princeton samples, table 1,
earlier in the text).

In almost all respects the constituents in these as-
semblages (table 13) are comparable to those described
earlier, but the following differences in mineralogy and
association should be noted :

1 These were collected at the north end of Moss Beach, approxi-
mately 2\ miles north of Princeton. The sandstones immediately
overlie course dioritic and granodioritic conglomerates which in
turn rest upon Montara intrusive rocks.

-'These averaged 2.6 percent of the total samples employed.

Table 1.1. Mineral frequencies in henry residues from hroirii
sandstones ill Hir 1/ creed foriiiiifion,

—(in + 11.% — un

Apatite 1 1

Augite i»

Biotite 1

Clinozoisite-epidote 4 4

Composites (5+ "i

(Jarnet 1

tllaucophane 1 1

Hornblende, green 7 — <>-f-

Hornblende, brown 5 4

Hornblende, oxy-type 4 2

Hypersthene 4 6+

Kyanite 1

Opaque minerals (incl. chromite) 1 5

Rutile 1

Sphene 2 4

Staurolite 1

Zircon 1 1

Zoisite 1

Doubtful identification _ 1

(1) Habit of fbe constituents of the assemblages, irrespective
of grain-size, is dominantly angular and accordingly this leads one
to surest that vectorial solution of pyroxene and aniphibole frag-
ments is actually taking place in these sediments, and is a normal
process of the weathering of such material.

(2) Brown and green hornblendes are often mere relicts within
wide peripheral zones of later formed colorless tremolite. This is
most suggestive of a transformation of hornblendes of igneous and
other origin into non-aluminous amphiboles, or at least amphi-
boles with a minimum of four-coordinated aluminum, that are
stable at the low temperatures and pressures of sediments.

(3) Semi-nephrites were found among the composite fragments.

(4) Rare deep red-brown biotite has a wide optic axial angle
(2V = 48°±2°) and such pronounced dispersion that basal plates
do not go into extinction between crossed nicols, but instead merely
change from red to greenish-blue on rotation of the microscope
stage.

(.">) Staurolite and kyanite, both representative of a high grade
of metamorphism are present.

Montara quartz diorite crops out over a wide portion
of the distributive province at the northern end of the
area treated here and heavy fractions prepared from
22 samples, though exceedingly small in volume, con-
tained the following: hornblende, biotite, zoisite, clino-
zoisite-epidote, colorless zircon, sphene, opaque iron
oxides, and very rare monazite ; thorite was not found
in any of these assemblages.

"When distribution of augite was discussed earlier,
attention was called to the dominance of augite in the
— 250 mesh fractions of sands found on beaches between
the outlets of Butano, San Gregorio, and Pomponio
Creeks, when ordinarily it is a relatively unimportant
constituent of that size fraction. Accordingly a number
of sediments cropping out near and within the drain-
age areas of those streams were studied. As a result
so-called sandstones reportedly belonging to the Puri-
sima formation and cropping out as prominent cliffs
north of the mouth of San Gregorio Creek were found
to consist almost entirely of finely comminuted rhyolite
glass particles (n = 1.497 - 1.503; dominantly 1.500; see
George, 1924, pp. 365, 368). Furthermore, the heavy
mineral assemblages separated therefrom consisted
largely of euhedral grains of augite and hornblende
averaging less than 62 microns in diameter. Clearly
then, these pumice silts, together with contribtttions
from local pillow lavas, have provided much of the
fine-grained ferromagnesian constituents found in near-
by sands.

CALIFORNIA DIVISION OK MINES

[Special Report 39

fractionation of samples of granitic rocks from the
Monterey - Pacific Grove area yielded monazite with
physical and chemical properties closely resembling those
o!' monazite separated from neighboring sands. Thus
it is suggested that the detrital monazite must owe its
origin to disaggregation of local granitic rocks, a con-
clusion strengthened by the knowledge that both garnet
and biotite of the sands and the intrusives are strictly
comparable. Thorite was not detected in residues pre-
pared from any of the granitic rocks, nor in. the local
beach sands for that matter.

At a later date, study of the minor accessory con-
stituents of the sedimentary rocks of the Coast Ranges
is contemplated in order to arrive at a clearer under-
standing of their mineralogy and thus to determine so
far as is possible what is their contribution to local
beachsands. But at this time no specific suggestions are
offered concerning origin of thorite, tantalite, ehrys-
oberyl, scheelite, and other minor constituents recog-
nized during tins study.

REFERENCES

Arnott, Ronald J.. 1050, X-ray diffraction data on some radio-
active oxide minerals: Am. Mineralogist, vol. 35, pp. 380-400.
Bannister, F. A., and Home, J. K. T., !!>.""><), A radioactive
mineral from Mozambique related to davidite : Mineralog. Mag.,
vol. 20. no. 200, pp. 107-112.

Berthois, Leopold, 1935, Recherches sur les inineraux lourds
des granites de la partie orientale du Massif Armoricain : Societe
Geologic et Mineralogie de Bretagne Mem., vol. 2, pp. 1-100.

B0ggild, (). I'... 1030, The shell structure of the mollusks : Mem.
de l'Acad. Roy. des Sciences et des I.ettres de Danemark, Copen-
hague, Sect, des Sciences, ser. 0, vol. 2. no. 2, pp. 231-326.

Bowie, S. II. I'., 1!)40 in Davidson. O. F., A prospector's
handbook to radioactive mineral deposits, Geological Survey and
Museum, London, 2S pp.

Broughtou, H. J., Chadwick, L. C., and Deans, T., 1050, Iron
and titanium ores from the Bukusu Hill alkaline complex, I'ganda :
Colonial Geology and Mineral Resources, vol. 1, no. 3, pp. 202-
2(56. His Majesty's Stationery Office, London.

Chapman, R. \V., and Williams, ('. R., 1035, Evolution of the
White Mountain magma series : Am. Mineralogist, vol. 20, pp.
502-530.

Curtis, (!. II., Evernden, J. F., and Lipson, J.-, 1058. Age
determination of some granitic rocks in California by the potas-
sium-argon method: California Div. Mines Special Rept. 54, pp.
1-1G.

Deer, W. A., and Wager, L. R., 1038, Two new pyroxenes
included in the system clinoenstatite, (dinoferrosilite, diopside and
hedenbergite : Mineralog. Mag., vol. 25, no. 160, pp. 15-22.

Dixon, B. E., and Kennedy, W. („>.. 1933, Optical uniaxial
titan-augite from Aberdeenshire: Zeitschrift fur Kristallographie,
vol. Si;, pp. 112-120.

Dupnrc, F., and Pearcc, F., 1007, uber die Ausloschungs-Winkel
del- Fliiehen einer Zone: Zeitschrift fur Kristallographie, vol. 42,
pt. 1. pp. 34-46.

Edelman, C. II., and Doe-las. D. J., 1032, Relikfstruktren
Detrifischer Pyroxene and Amphibole : Tsehennaks mineralogische
und petrographische Mitteilungen, vol. 42. pts. 5-6, pp. 482-400.

Evans, l\, Haymnn, II. .1., and Majeed, M. A., 1034, The graph-
ical representation of heavy mineral analyses: Geo!., Min. Met.
Soc. India Quart. Jour., vol. (i. no. 2, pp. 27-47.

Flint, E. P., ami Wells, L. S., 1041, Relationship of the garnet-
hydrogaruet series to the sulphate resistance of portland cements:
Natl. Bur. Standards, Jour. Research, vol. 27, pp. 171-180.

Frondel, ('., 1040, The dufrenite problem: Am. Mineralogist,
vol. 34, pp. 513-540.

Frondel, C, 1053, Hydroxyl substitution in thorite and zircon:
Am. Mineralogist, vol. 38, pp. 1007-1018.

Geller, R. !•'., 1041, A resistor furnace, with some preliminary
results hi) to 2000° C. : Natl. Bur. Standards, Jour. Research, vol'.
27. pp. 555-566.

George, D. II., 1051, Thorite in California: Am. Mineralogist,
vol. 3<i, pp. ]2!>-i:>,2.

A9232;; 2-5H 3,500

George, W. ()., 1024, The relation of the physical properties of
natural -lasses to their chemical composition: Jour. Geology, vol.]
::2, pp. :;53 -372.

Cutzeil, (!.. 1042, Determination and localization of metallic min-
erals by the contact-print method: Am. Inst. Min. Met. Eng.,
Tech. Pub. 1457.

Henry, N. E. M., 1035, Some data on the iron-rich hypersthenes :
Mineralog. Mag., vol. 24, no. 151, pp. 221-220.

Holmes, A., 1031, The age of tlie earth: Natl. Research Coun-
cil Bull. 80, pp. 124-45!). (Physics of the Earth, vol. IV.)

Hutton, C. (»., 1943, Hydrogrossular, a new mineral of the
garuet-hydrogarnet series : Royal Soc. New Zealand Trans., vol.
7.">. no. 3, pp. 174-1 SO.

Hutton, C. O., 1045, The iron-sands of Fitzroy, New Plymouth :
New Zealand Jour. Science and Technology, vol. 26, no. 6, see.
P., pp. 201-302.

Hutton, C. O., 1050, Studies of heavy, detrital minerals: Geol.
Soc. America Bull., vol. 61, pp. 635-716.

Hutton, C. ()., 1051, Allanite from Yosemite National Park,
Tuolumne County, California : Am. Mineralogist, vol. 36, pp.
233-248.

Hutton, C. O., 1052, Accessory mineral studies of some Cali-
fornia beach sands: U. S. Atomic Energy Commission RMO
981, mimeo.

Johnson, R. W., 1040, Clinozoisite from Camaderry Mountain
County Wicklow : Mineralog. Mag., vol. 28, no. 204, pp. 505-515j
Kunitz, W., 1930, Die Isoinorphieverhaltnisse in der Horn-
bh'iidegruppe : Neues Jahrb.. Beilage-Band 40, pp. 171-250.

Lawson, A. C, 1014, V . S. Geol. Survey Geol. Atlas, San Fran-
cisco folio (no. 103), 24 pp., 15 maps.

I.indberg, M. L., 1040, Erondelite and the frondelite-rockbridgeite
series : Am. Mineralogist, vol. 34, pp. 541-540.

Mackay, R. A., 1051a, The detection of columbite by ultra-
violet light : Inst. Mining and Metallurgy Bull., vol. 60, pt. 4,
no. 530, pp. 120-131.

Mackay, R. A., 1051b, The detection of columbite by ultraviolet
light; Report of Discussion of earlier paper: Inst. Mining and
Metallurgy Bull., vol. 00, pt. 6, no. 532, pp. 248-255.

Mawson, D., 1916, Mineral notes: Royal Soc. South Australia
Trans., vol. 40, pp. 262-266.

Mawson. 1)., 1044, The nature and occurrence of uraniferous
mineral deposits in South Australia: Royal Soc. South Australia
Trans., vol. 68, pp. 334-357.

Milner, II. B., 1040, Sedimentary petrography, Thomas Murby
and Co., London, 3d ed.

Nockolds, S. R., 1047, The relation between chemical composition
and paragenesis in the biotite micas of igneous rocks: Am. Jour.
Sci., vol. 245, pp. 401-420.

Palache, C, P.erman, II., and Frondel, C, 1040, The system
of mineralogy, 7th ed., vol. 1, John Wiley and Sons, Inc., New
York.

Ridgway, Robert, 1012, Color standards and color nomenclature.
Washington, I). C.

Ross, C. S., Miser, II. I)., and Stephenson, L. W., 1020, AVater-
laid volcanic rocks of early Upper Cretaceous age in southwestern
Arkansas, southeastern Oklahoma, and northeastern Texas: IJ. S
Geol. Survey Prof. Paper 154-F, pp. 175-202.

Schoeller, W. R., 1037, The analytical chemistry of tantalum
and niobium, Chapman and Hall, Ltd., London.

Strunz, Hugo, 1040, Mineralogische Tabellen, Akademisehe Ven
lagsgesellschaft, (Jeest und Portig K.-G., Leipzig.

Tyler, S. A., and Marsden, R. W., 1038, The nature of leu
coxene : Jour. Sed. Petrology, vol. 8, pp. 55-58.

Tyler, S. A., Marsden, R. W„ Grout. F. F., and Thiel, G. A.
1040, Studies of the Lake Superior Preeambrian by accessor]
mineral methods: Geol. Soc. America Bull., vol. 51, pp. 1420
1538.

Van Andel, Tj.H., 1050, Provenance, transport and depositioi
of Rhine sediments, II. Veenman and Zonen, Wageningen, 120 pp
Vincent, H. C. G., 1051, Mineral separation by an electro
chemical-magnetic method : Nature, vol. 167, no. 4261, p. 1074.

Wentworth, C. K., 1022, A scale of grade and class terms foi
clastic sediments: Jour. Geology, vol. 30, pp. 377-302.

Williams, D., and Nakhla, F. M., 1051, Cbromographic contac
print method of examining metallic minerals and its applications
Inst. Mining and Metallurgy Trans., vol. 60 (for 1050-51), pt
7, pp. 257-205.

Winchell, A. N.. 1051, Elements of optical mineralogy, pt. II
4th ed., John Wiley and Sons, Inc., New York.

Zastawniak, F., 1051, Chemical composition of biotites in dif
ferent rocks of the Tatra Mountains: Rocznik Polsk. Tow. Geol.
vol. 20 (for 1050), pp. 117-158; esp. pp. 145-158.

printed in California state printing offici