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1 2 3

£!rrata.—'\. In analysis vi., p. 11, the oxygen of 2'7.'72 of alumina
should be 12.96, instead of 13.95. This correction being made, the
oxygen ratios for the protoxyds, sesquioxyds and silica become
7.62:13.73:23.26=1:1.80:3.05, instead of 1:1.93:3.05. In this case
therefore, as well as in analysis vii., there is present a certain excess of
protoxyds and silica corresponding nearly to a ter-silicate.

2. On page 18, line 20, for 32.22, read 38.22.

CONTRIBUTIONS

TO THE HISTORY OF

EUPHOTIDE AND SAUSSURITE

T. STEKRY HUNT,
Of the Geological Survey of Canada.

[from the AMERICAN JOURNAL OF SCIENCE, VOL. XXVII, MAY, 1859.1

ON EUPHOTIDE AND SAUSSURITE.

1, The name of euphotide was originally given by Ilaiiy
to a rock composed of diallage and a white compact mineral
which he designated as feldspath tenace, (the compact feldspar of
Werner, the Icmaniteof DeUuuetherie, and the jade of de Saussure
senior). The well-marked contrast of colors which suggested
the name of euphotide is seen in the beautiful verde di Corsica
or verde antico di Orezza, and in some varieties of the rock from
Mt. Rose. In these the diallage is represented by a grass-green
smaragditc, and this mineral and hypersthene being regarded
by Haiiy as varieties of diallage, he included under the head ol
euphotide, the verde di Corsica, (for which alone d'llallov re-
tains the name of euphotide,) the hypersthenite or hyperite of
other authors, and the granitone of the Italians. This last by
an error of Von Buch, in which he has been followed by GustaV
Rose, is very frequently called gabbro. 'J'he true gnbbro of the
Italians is however a diallagic ophiolite. (Brongniart, Classif.
des Roches, 1827, p. 75.)

Brongniart defines euphotide to be a mixture of diallage with
jade, petrosilex, or compact feldspar, and including d'llalloy's
two species, euphotide and granitone, but excluding hyperite,
he distinguishes as varieties, jadian and feldspathic euphotides,
besides ophitic (serpentinous) and micaceous euphotides, the
latter being sometimes talcose.

Coquand {Traite des Roches, 1857,) has followed Ilaliy with re-
gard to the euphotides, while Senft {Die Fekarien, 1857,) places
in one group, under the head of hyperite, three genera, eclogite,
gabbro, and hypersthenite, in the second of whic' he includes
rocks made up of labradorite or saussurite with diaiiage or sma-
ragditc. The eclogite of Haliy is composed of diallage or sma-
ragditc, and red garnet ; it often holds disthene (cyanite) through
the predominance of which it passes into disthenite (disthenfels),
while hypersthenite or hyperite (hypersthenfels, G. Rose) is a
mixture of saussurite or labradorite with hypersthene (d'Halloy,
Senft.).

Distinctions like some of the above based upon the contained
varieties of pyroxene are evidently of secondary importance,
and it becomes necessary to define with more strictness the na-
ture of the other element of the rocks in question. The jade
of the Swiss Alps to which de Saussure junior, afterwards gave
the name of saussurite, was described by de Saussure senior, as
compact, tenacious, greenish-white in color, hard enough to
scratch quartz, and having a specific gravity of 3-318 — 3-389.

T. S. Hunt on Euphotide and Saussurite,

Mohs gives 3*256 for the density of a granular saussurite from
Peidtnont, and 3-34 for a compact variety from the Canton of
Vaud, while Naumann assigns to the mineral a density of 3-40.
These authors thus agree in ascribing to saussurite a specifio
gravity much above that of the feldspars.

Kiaproth and de Saussure junior, both analyzed specimens of
the saussurite from the shores of the Lake of Geneva (lemanite,
I and Ti) while Boulanger subsequently examined the saussurite
from the euphotide of Mt. Genevre (iii), and from two localities
in Corsica, the valley of Orezza (iv) and tL; banks of the Fiu-
malto (v).

Silica,

Al'imina,

Peroxyd of iron,

Lime,

Magnesia,

Soda,

Potash,

4900

2400

6-50

1050

8-75

5-50

9926

II.

44 00

30-00

12-50

4-00

• • • *

6-00
•25

ni.

44-6
30-4

'155
2-5
7-5

96-75* lOOo

IV,

43'6
320

'2*1 -0

2-4

' V-6
100-6

340
244

Si's

6-4

96-6

The physical and chemical characters of the above specimens
offered considerable dificrences. The saussurite 11. is described
by de Saussure as leek-green, subtranslucent, w^^h an oily lustre,
and a finely granular, scaly fracture ; it scratched quartz and
had a density of 3-261. At a high temperature it fused without
loss of weight, into a glass much softer than the original mine-
ral, and having a density of only 2-8. This saussurite, which
was free from any admixture of smaragdite, was scarcely attacked
by boiling sulphuric acid. — (Journal des Mines, vol. xix, p. 205,
A. D. 1805.)

The saussurite from Mt, Genevre (iii) according to Boulanger
is associated with a greenish-brown smaragdite, and is itself
greenish-white and compact, not scratched by the knife, and
having a density of 2-85. He describes another euphotide from
the same locality as having a lamellar base, with cleavages like
feldspar, sometimes chatoyant, hard, not attacked by acids, and
with a density of 2-58. The analysis of this undoubted feld-
spar gave him, silica QQ% alumina 18-5, lime 1'8, soda 6-0, pot-
ash 4-3 = 97-2. ^

The euphotide of Orezza is described by Boulanger as com-
posed of green diallage, a blackish matter also apparently a va-
riety of diallage, and saussurite, the whole arranged in parallel
bands, giving to the mass, which is very tough, a schistose frac-
ture. The saussurite (iv) was very compact, less hard than in,
and had a density of 318. It was easily fusible and not attacked
by concentrated sulphuric acid.

* Besides 0'06 oxyd of manganese.
WSGOND SERIES, Vol. XXVII, No. 81.-MAY, 1869.
44

4 T. S. Hunt on Euphotide and Saussurite.

Tho euphotide of the Fiumalto consisted of green diallagc
with curved lamellae in a white paste, which was tender, easily
cut with a knife, and had a density of 3-80 (v). It was readily
fusible and easily attacked by sulphuric acid, with which the
analysis was made ; the separated silica being dissolved by a
solution of potash which left a residue, supposed to be diallage,
and equal to 8*8 parts, which added to the above analysis makes
'-he sum 1004; alkalies were absent— (^wtj. des Mines, (8J,

viii, p. 159.)

Notwithstanding the peculiarities presented by saussurite,
modern mineralogists have generally referred it to labradorite
or some other feldspar, (see Beudant, Bischoff, Dana, Delesse,
etc.). Jameson, separates it from the feldspars on account of
its greater specific gravity, but recent authors seem to have en-
tirely lost sight of this characteristic. Coquand describes saus-
surite as having a density of 2'87, while according to Delesse it
is seldom inferior to 2-80. These authors agree in declaring the
mineral to be decomposable by acids like labradorite, while
Bischoff and Senft, without alluding to its density, assert that
saussurite is not attacked by acids.

An analysis of saussurite by Stromeyer gives the composition
of labradori+,0, while Lory on the other hand has described as
euphotide a rock from Levaldens in the Dauphinese Alps, which
is made up of an olive hornblende and a white mineral having
the cleavage of a feldspar and the composition of andesine.
—{Bull. Sac. Oeol de France, [2], vii, 540.)

Delesse examined the white base of a euphotide from Odern
in the Vosges, and another from Mt. Genevre. Both of these
were highly crystalline and exhibited the polysynthetic macles
of the feldspars of the triclinic system. When pulverized and
treated with muriatic and sulphuric acids they swelled up and
were decomposed. Delesse has however described them as saus-
surite. That from Odern gave him, sihca 55-23, alumina 24-24,
lime 6-86, magnesia 1-48, protoxyd of iron 1-11, soda 4-83, pot-
ash 3-03, water and volatile matters 305 = 99-83. The eupho-
tide of Mt. Gencjvre contained diallage, a serpentine-like sub-
stance, and a ferriferous carbonate of lime, besides the feldspar,
whose crystalline laminae were more than one-third of an inch
in length, and gave by analysis, silica 49*73, alumina 29'65, lime
11-18, magnesia 0-56, protoxyd of iron 0-85, soda 4-04, potash
0-24, water and volatile matters 3-75 = 100-00. Of the volatile
portion according to Delesse, at least 2-50 p. c. is water, the re-
mainder being carbonic acid. {Ann. des Mines, [4], xvi, pp.
238 and 267.) This feldspar resembles that of the orbicular
diorite of Corsica which gave to Delesse, silica 48-62, lime 12-02,
alkalies 3-61, and 0-49 of water.

T, a. Hunt on EuphuUde and Saussurite.

Under the name of saussurite von Rath has described a mine-
ral which with hornblende (uralite) forms the greenstone of
Neurodc in Silesia. It liad the hardness, cleavage, and crystal-
line structure of labradorite, but with a specitic gravity of *J 90,
and gave by analysis, silica 50'84:, alumina 26"00, peroxyd of
iron 2-73, lime 14-95, magnesia 0-22, potash 0'61, sod'i. 4-68,
volatile 1*21 — 101'24. — {Pogg. Ann., xcv, 555.)

2. Accepting the view maintained by Rose, Bisclioif and De-
lesse, that saussurite is nothing more tlian a feldspar, I referred
to this species the compact feldspars of the liuurentian rocks of
Canada, described in my report of 1854. Associated with the
limestones and ophiolites of this most ancient geological series,
is a great body of crystalline stratified rocks, composed essen-
tially of anorthic feldspars, sometimes almost without admix-
ture, but frequently associated with green granular or cleavablo
pyroxene, which passes through a kind of bronzite into hyper-
sthene. Small quantities of epidote, garnet, and more rarely
mica and quartz, are also met with, and magnetite and ilmenite
are common. Different varieties of these rocks would be re-
ferred by lithologists to the species labradophyre, dolerite, and
euphotide. The feldspars are sometimes very coarsely crj'stal-
line but often compact ; they have a hardness of 6"0, and vary
in density from 2*67 to 2'73, and in composition from andesinc
to vosgite. The denser varieties are those in which lime and
alumina predominate; all of them contain besides soda small
quantities of potash. The analyses of numerous varieties of
these feldspars will be found in the Report cited above, and in
the L. E. and D. Philos. Magazine, [4], ix, 262.

The euphotides examined by Delesse and Lory are apparently
nothing more than varieties of dolerite, by which term we un-
derstand a rock composed essentially of a triclinic feldspar, with
some variety of pyroxene, which may be augite, hypersthene,
or diallage. According to G. Rose, smaragdite, which is the
variety of pyroxene regarded as characteristic of euphotide, has
often the external form of pyroxene with the cleavage of horn-
blende, constituting the variety uralite, while in the euphotides
of Baste and Yeltlin hornblende occurs with the diallage, and
sometimes replaces it entirely, giving rise to a rock composed of
saussurite and hornblende. Sandberger has observed crystals
of pyroxene forming macles with others of hornblende, and the
latter often surround the crystals of pyroxene, or as I have re-
marked in specimens from Madawaska, small crystals of deep
green hornblende are implanted upon large prisms of greenish-
white pyroxene. Smaragdite according to Ilisinger and Dela-
fosse consists of lamime of pyroxene and hornblende united in
a more or less regular manner. Since diorite is distinguished
from dolerite by the substitution of hornblende for pyroxene, it

T. S. Hunt on Euphotide and Saussurite.

is evident that feldspathic agf^regates like those of Baste present
a transition from the one to the other species oi" rock.

Diorite is distinguished from diabase according to Senft by
containing a feldspar insoluble in acids (albite or oligoclase,) and
by the frequent presence of quartz, while in diabase the feld-
spathic element is less silicious and decomposable by acids ; (lab-
radorite or a variety approaching anorthite) * When however
we consider the manner in which these feldspars pass into one
another, this distinction between diorite and diabase seems of
but secondary importance. We have seen that the orbicular
diorite (or diabase) of Corsica contains a feldspar near anorthite
in composition, while others in the Vosges, according to Delesse,
contain labradorite and andesine, the latter with quartz. Lory
has described a diorite from the cj-ystalline schists of the moun-
tains of Chalanches (Is^re) which is made up of a chromiferous
hornblende, with crystalline andesine and a pale greenish-yel-
low epidote often intimately mixed with the feldspar, and so
abundant as to characterize the rock. This epidote gave by
analysis, silica 40'6, alumina 302, lime 17*7, protoxyd of iron
11-2 = 997.

3. Diorites, as already mentioned, sometimes contain albite.
Associated with the Silurian ophiolites of Canada we often find
beds of rock which are mixtures of albite with hornblende or
pyroxene, sometimes with small portions of carbonates. These
diorites are tough, granular, sub-translucent, greenish or bluish-
gray in color, weathering superficially to an opaque white and
having a somewhat waxy lustre. Hardness 6*0; density 2"71 —
2'76. The hornblendic element is sometimes nearly amorphous,
but at other times forms cleavable grains ; by ignition these
portions become darker, while the feldspar is rendered whiter
and more opaque, and often exhibits striae upon the cleavage
surfaces.

A fine grained variety of this diorite from Orford was exam-
ined ; it had a somewhat yellowish-green color and a subcon-
choidal fracture. After ignition the striated crystalline grains
of feldspar were distinctly seen. The powdered rock does not
effervesce with nitric acid, which appears to be without action
upon it. The analysis gave as follows :

Oxygen.
Silica, 63-60 63-40 83-81

[

Alumina 12-70

Soda, 7-95

Potash -13

Lime, 7-28 7-50

Magnesia, 3-37

Protoxyd of iron, 4-23

Loss by ignition, '40

99-68

• See R. H. Scott, L. K and J). Phil. Mag., [4], xv, 618.

2-14

1-35

•94

6-93
207

4-43

r. S. Hunt on Eupholide and Saussurite. 7

form a pyroxene.* '" "^"'' ""-' P'-°P<>"iou required to

tiIt'^ev:lfr*'M,trtl,t1fL™<' dolentio .rocks i, some-
which may be regiS as a mixtu^' „f f fT' '°"? P^'^ilcx,
perhaps a-'distinet feldVar li^e 1 nblkl B P'" "■'* l"""^' »
petrosilex as sometimes formf,,,, nit ^^I'S"''"' mentions
'Thompson has dcSed uX U.c nL^"^? "^ O'^fhotido, ar.d
which occurs with dialla^e at thp T ifl ^aussunte a mineral
density of 2-80, and'yteTdifg" ^^X" StTfo' ''r",'^ "

- of two TaSes °o? ^eiX' "'Trc l^r^'r" ^ ''"'"^■•
beds among the opiiiol te rooks of Orfor,! iP "' S^'?'

'cTfoSMii-.ri^'rr-^^^^^^^

just described by the atence of th'wT-f^''' '^^°'" "^^ '^''°"^
the weathered surfaces Cofnrl„- 1'" "P'"J"f '^""'"K "Pon

waxy, dull. H:rftss6ofdS"l'.63°^«^o%',1-*^''^! '-'™
(b) from St IfPTiri' ia o 4- 7''"'='^''/ ^,odo— 2 639. The second

oeiurs ?nte strSd wfth S; ^™™>r «'-'=^»'''' ™k. which
Silurian strataThich are ri^'rir^ l™estones in unaltered
ophiolitie series. It ksomewSi "' "'" '"l"'™'™'^ of the
the M which howe'eTuTlt^y^eZbTs''"' tenacious tha.

Silica

^'•jmina,

Soda

Potash,

■Lime

Magnesia

Protoxyd of iron,
Loss by ignition, .

'78-40
11-81
4-42
1-93 .
•84 ,
•77 ,
•72.
•90.

71 •40

13 60

331

•84
2-40
324
250

rocks

"WTi"7 9979 99'C6

™sLuti^-rrtS:f^^j:^rs±r^„^

t T. S. Hunt nu Kupholide and Sau.saurUf.

de SuuBsnro and Melis. At l(<n.irth I met with a vory lu-avy
rock which occurs with tho ophiolitcs of Orlbrd, and chwely re-
sembles nil ophitic eiii>hotide. It ia mudc iip of a white garnet
having the aspect of suiissurite, intermingled with u small
amount of a soft green serpentine, which tills tho interstices
between irregular roundetl mt'SHt'S of the garnet; portions of tho
latter mineral half an inch in diameter, are easily obtained in u
state of purity. It is distinguished by a hardness of 7-0, and by
its density, which for selected fragments, was found to be; 8'522
— 3-636. It is amorphous, linely granular, and extremely tena-
cious, with a conchoidal fracture ; lustre feeble, waxy ; color
yellowish or green ish-white ; sub-translucent. After intense ig-
nition, which did not however effect its fusion, the pulverized
mineral gelatinized with, hydrochloric acid. Its analysis was
made after fusion with carbonate of soda, and gave :—

Silica 88;60 38-80

Alumina '2271

Lime a-l'SS

Magnesia '^^

Oxyds of iron and nmiiganese I'^O

Soda and a trace of potasli '+7

Loss by ignition, ^'^Q

y980

This mineral agrees closely in composition and properties with
lime-alumina garnet, whose theoretical composition is represented
by silica 401, alumina 22*7, lime 37-2 = 100-0. Croft obtained
for a white garnet from the Ural mountains, having a density of
3-504: silica 36-86, alumina 24-90, lime 37-15 = 98-10.

At the falls of the river Guillaume in St. Fran(;ois, (Beauce,)
there is also found a heavy rock which is composed in great part
of garnet. It forms a bed in contact with an ophiolite, and has
a somewhat variable aspect ; in some portions it has a sub-con-
choidal fracture with traces of crystallization ; lustre shining,
somewhat silky, color yellow ish-white, sub-translucent. This
variety, which is apparently homogeneous and exceedinglv
t<" .gh, has a hardness of 7-0, and scratches deeply the surface of
agate ; its specific gravity was found to be 3-333 — 3-364. It also
occurs as a greenish-white or grayish-white somewhat granular
rock, cavities in which are lined with small indistinct crystals ;
the density of this variety was 3*397 — 3-436.

Other specimens from the same locality exhibit the garnet
intermingled with large cleavable masses of dark-green horn-
blende, which passes into a pearl-grey or lavender-grey variety.
Small fragments of the garnet from this mixture had a density
of 3 496; thev were white, opaque, with a conchoidal fracture,
and somewhat vitreous lustre. Intermingled with the garnet and ■
hornblende, was another white or yellowish-white amorphous
mineral, with a waxy lustre and a hardness of 6-0; tho density

T. S, Hunt on Euphotuh and Saussurile.

of a nearly puro specimen of it wns 2-720, of anotlior fragnunit
2*823. This, conj' ncd with its hanhu'ss, rcTidcns it proV)ablo
that it ia a fbhlsjA.. ; l)iit it is very <liHicMlt to separate it from
the garnet, or oven to distinguisli bctwcfii tlic two species by
the eye alone. Another specimen of a white granular roek from
the same locality, wiiieh had been taken for garnet, had a density
of oidy 2'80O, and was supposed to bo ehii-lly leldspjithic in ita
nature. The specilic gravity of the grevish hornblende was
S046. "

A specimen of the first described variety, having a density of
8'883 was selected for analysis; its powtlcr did not ell'ervesce
with heated nitric acid, which however dissolved from it consid-
erable alumina and lime. By the ignition of the rock, ita
yellowish color was only changed by the appearance of rare
points of black ish-grcen. The analysis gave as follows:—

Oxygen.

Silica 4486 28 69

Alumina, 1076 6 08

Peroxyd of iron 820 '96

Lime 3438 9 77

Mngnesin, 5'24 2 09

Loss by ignition, 1 -10

99f.3

If we suppose the alumina the peroxyd of iron and a portion
of lime to form a garnet in which the oxygen ratios of the pro-
toxyds, sesquioxyds and silica are 1 : 1 : 2, the residual lime and
silica with the magnesia will be in the proportions requisite to
form a pyroxene. We have lime 21*07, alumina 10*76, peroxyd
of iron, 3*20, silica 22-69=57*72, with the oxygen content 5*99 :
5*99 : 11-98. There remains then for the pyroxene, lime 18-31,
magnesia 5-24, silica 22-16=40-71, containing oxygen 5-87 and
11*71 = 1 : 2. The observed density of the rock corresponds
very closely with that calculated for a mixture of lime-alumina
garnet and pyroxene in the above proportions. — (^Oeol. Survey of
Canada, Keport, 1856, p. 449).

5. The great density of the above described garnet rocks and
their association with hornblende, serpentine and feldspar, led
me to suppose that similar rocks might have furnished to different
chemists some of the discordant facts which are met with in the
history of euphotide a. id saussurite. I have recently, however,
through the kindness of Prof. Arnold Guyot, now ojf Princeton,
New Jersey, had an opportunity of examining a collection of the
euphotides of Switzerland, made by him in the course of his
researches on the distribution of the erratic rocks of the basin of
the Rhone. Prof. Guyot then traced the euphotides, which are
found in scattered blocks and pebbles for a distance of nearly
one hundred and fifty miles, to the valley of Sass, or rather to
the corresponding chain of the Sassgrat, which forms a part of

T. S. Hunt on Euphotide and Saussurite.

Mt. Rose.* Thf^ euphotides of the Alps according to other ob-
servers are associated with protogine, ophioHtes and crystaUine
schists.

I had now before me the original euphotides which had been
studied by Haiiy and de Saussure, and through the liberality of
Prof Guyc t was furnished with numerous specimens of the char-
acteristic varieties. Their examination has afforded me the
following mineral species: saussurite, smaragdite, actinolite, talc,
feldspar, and rarely pyrites.

The saussurite, which is generally predominant, is very uni-
form in its charactei's ; it is always finely granular or compact,
very tough, and with a sub-conchoidal or splintery fracture. Its
color is white, passing into greenish bluish and yellowish-Avhite,
rarely with flesh -red stains ; sub-translucent ; lustre feeble, waxy.
Hardness 7*0; scratches quartz. Specific gravity 3'33^—3*38. A
euphotide containing cleavable masses of smaragdite an inch in
diameter, afforded me portions oi" bluish-white saussurite, appa-
rently homogeneous, and having a density of 3*336 — 3*365.
Another specimen of euphotide, containing a g'ood deal of talc,
and only small grains of smaragdite, had a density in the mass
of 3*315, ^''ut selected fragments of the saussurite gave the
number 3 •385. Another large fragment of greenish-white saus-
surite had a specific gravity of 3*338, while a fourth specimen of
euphotide holding only small lamellai of smaragdite, and min-
gled with greenish-gray talc, had a duunctly granular texture,
and a density of only 3*16 — 3*20.

The smaxUgdite of all these varieties of euphotide has a grass
green color passing into emerald and olive-green. Lustre some-
what pearly; hardness 5 5; specific gravity of fragments from
the first-mentioned euphotide, 3*10 — 3*12. The smaragdite gen-
erally exhibits only the cleavages of pyroxene, but in some cases
it is irregularly penetrated by slender prisms of hornblende.

Talc is rarely absent from these euphotides, and is often abund-
ant in small foliated or radiated masses, enclosed in the saussu-
rite. The talc is generally silver- whitv^, but occasionally appears
greenish from the presence of minute crystals of dark green
actinolite, which m.ay be seen penetrating the talc, in close prox-
imity to the yellowish-green smaragdite. The latter I have
alwa'^'s found enclosed 'a the saussurite.

A bluisi;-gray or lilac feldspar is often met with in these
euphotides, and is at once distinguished from the saussurite by
its color, cleavage, translucencv, vitreous lustre, and inferior
hardness. I have riot observed cleavage fiices of this feldspar
more than a fourth of an inch in length, although in some speci-
mens it is rather abundant. Grains of it are sometimes imbed-
ded in the talc, but it more generally occurs in the saussurite.

* See also .'«. Forbes, travels through the Alps, p. 852.

T. S .Hunt on Euphotide and Saussurite. 1 1

This feldspar is completely decomposed by heated sulphuric acid
and contains a large proportion of lime, characters which show
It to be labradonte or an allied variety.

Two specimens of saussurite were selected for analysis the
biuish-white variety from the first mentioned euphotide having
a specific gravity of 3-365, (vi) and selected ihi-ments of a
greenisn-white variety from the second, with a densTty of 3-885
(VII). Ihis was penetrated by talc, from which it was impossi-
ble, completely to separate it. The eleutriated mineral was
decomposed by prolonged fusion with carbonate of soda, the
separated sihca and alumina being in each case carefully an-
alyzed Thetalkalies were determined by J. Lawrence Smith's
method of igniting with carbonate of lime and sal-ammoniac.
and consisted of soda with but traces of potash. The results
were as follows :

V!. Oxygen. vn.

43-59 23-25 48-10

27-72 13-95 25-34

2-61 -78 3-30

la-71 6-63 12-60

2-98 119 6-76

8-08 -80 8-65

■36 .... -66

Silica,

Alumina,

Peroxyd of iron,

Lime,

Magnesia,

Soda,

Loss by ignition.

Oxygen.

25-65

11-94

•99

3-60

2-70

-91

100-04 100-31

Boiling concentrated sulphuric acid removed only traces of
alumina and lime from the pulverized saussurite, which was
However partially decomposed by this acid after liavino- been
strongly ignited. o ^ "

The hardness and specific gravity of saussurite assign it a
place with epidote. Eammelsberg has recently ])ublished the
analyses of six varieties of lime-alumina epidote or zoisite, vary-
ing in density from 3-25 to 3-36, and finds the oxygen ratios of
the protoxyds, peroxyds and silica to be nearly as 1 : 2 : 3, often
however with an excess of silica. The ratios of his analyses
vary between the limits 1 : 1-94-2-16 : 2-95-3-36.-(i^erZm Acad.
Btr. 18o6, 60o).

If we follow Eammelsberg, who has regarded the small
amount of iron in tne zoisites, as peroxyd replaein- alumina, we
Have lor the analysis vi the ratios 762; 14-78 • 9^-95^1 . 1-93 .
3-05 while for VII we have 7-21 : 1293 : 2565, showing an ex-
cess both ol sihca and protoxyd, due to the intermingled talc.
it we re,^ ird this surplus of protoxyd as magnesia it would
equal 5-/0 per cent of talc, and deducting the elements of this
from the analysis we have for the oxygen ratios of the saussu-
rite the numbers 1 : 2 : 3-29. Saussurite has then the hardness,
specific gravity and chemical composition of a lime-alumina epi-
dote or zoisite, containing small portions of nmcrnpsia nnj eoda
which arc Irequently present in this species. The analyses of

8EOOND SERIES, Vol. XXVII, No. 81. -MAY, 18S9

T. S. Hunt on Evphotide and Satissurite.

various epidotes give from two to six per cent of magnesia, and
from one to more than two per cent of soda.'* — (See Dana's
Mineralogy, 4th Ed., ii, 407).

6. The composition of zoisite as already noticed by Kammels-
berg is identical with that of meionite, a species which is shown
by its hardness of 6-0 and its density of 2-6— 2-7, to belong to
the dimetric division of the feldspar group, where it is to the
scapolites what anorthite (with the ratios 1 : 3 : 4,) is to the tri-
clinia feldspars. The mineral described by Boulanger as saus-
surite from Mt. Genevre, with a density of 2 '65, gives according
to his analysis (iii) the oxygen ratios 7*37 : 14-18 : 23-75= 1 :
1-91 : 2-22, and appears to have been meionite. In de Saussure's
analysis, (ii) if we regard the iron as protoxyd, we obtain the
ratios 5-22 : 14-02 : 23-50, but there is then a deficiency of 4*60
p. c. in the analysis of an anhydrous mineral. Klaproth's re-
sults (i) seem to indicate a mixture of a silicate like pyroxene or
talc as in vii, while the anomalous softness of V and the facility
with which it is decomposed by acids, render it difficult to form
any conclusion about the saussurite of the Fiumalto examined
by Boulanger. His analysis of the saussurite of Orezza (iv)
gives the oxygen ratios 7-23 : 14-95 : 23-25=1 :2;06 : 3-21, so
that it has the composition of meionite and zoisite, while its
specific gravity is between the two. Although inferior in hard-
ness, it resembles zoisite in resisting according to Boulanger the
action of concentrated sulphuric acid.

The saussurite of Orezza evidently demands farther study ; it
remains to be seen whether the verde di Corsica or verde antico di
Orezza, as it is also named, (the corsilite of Pinkerton, Petralogy,
ii, 78), which is regarded by d'Halloy as the typical euphotide,
is not distinct from that of IMt. Rose. Delesse found the specific
gravity of the Corsican euphotide to be only 3-10. The name

* Laurent in nn essay on the silicates published in 1849, insisted that distinctions
based on the relations between the proportions of protoxyds and sesquioxyds are of
but secondarj' importance, since these oxyds may replace each other to an indefinite
extent in many silicates, without altering the mineral type. This principle Laurent
then illustrated by the epidotes among other species, showing from Hermann's
analyses of tlr;.een specimens (of which the analyst had made three subspecies,)
that although the oxygen ratios of the protoxyds and sesquioxyds oflfered considera-
ble variations, it was possible by admitting the substitution of the one for the other,
to reduce all these epidotes to the same formula with garnet, SiOjRg, i.e.,
SiO+RO, in which RO, represents both protoxyds like CaO, and sesquioxyds like
alO(=:Al2 0:,-^3).— (C'omn/es Rendns dcr Travaux dc Chcmie, 1849, p. 277).

TJiis idea of Laurent although at the time rejected, is now universally admitted.
Dana has adopted it in the 4th Ed. of his Mineralogy; Hermann has recently re-
viewed his own analyses and accepts Laurent's view, while Rammelsberg who illus-
trated it in his laborious researches on the tourmalines, has recently applied it to the
augites and hornblendes containing peroxyd of iron. But while there is no doubt of
the general and wide application of this principle of the homopmorphism of pro-
toxyds with sesquinxvds. it is nevertlieless true as Dana hns remarked, that in the
epidotes the variations in the oxygen ratios of the protoxyds, sesquioxyds and silica
are about 1:2: 3, which may be loi '<ed upon as the normal ratio for epidote, at
1 : 1 : 2 is for garnet, and 3 : 2 : 5, for idocrase. — (This Jour., [2,1 xxv, 406).

T. S. Hunt on kotide and Saussurite.

esia, and
e Dana's

lammela-
is shown
)elong to
s to the
) the tri-
as saus-
ecording
S-75-=l:
aussure's
)tain the
r of 4-50
oth's re-
Dxene or
e facility
'j to form
xamined
;zza (iv)
3-21, so
diile its
in hard-
,nger the

itudy; it
antico di
■^etrahgy,
iphotide,
i specific
he name

distinctions
xyds are of
n indeiinite
)le Laurent
Hermann's
ub species,)
1 considera-
r the other,
2R3, i. e.,
ioxyds like
277). _
f admitted,
■ecently re-
f who illus-
ed it to the
no doubt of
ism of pro-
that in the
s and silica
epidote, at

of verde di Corsica, which he arts is applied to the rock as a
whole, is by Beudant resti, to the contained smaragdite.

I have lately examined . pule yellowish-green compact and
apparently homogent^ous rock, which forms great beds among
the crystalline schists of the Shickshock mountains in Gasp6,
and has somewhat the aspect of saussurite. Its hardness is 7*0
and its density 3-04: — 3-09. It is exceedingly tough and sono-
rous, has a conchoidal fracture with a feeble waxy lustre, and is
translucent on the edges. The analysis gave as follows :

Silica

Alumina, 12'30

Protoxyd of iron, 940

Lime 14-10

Magnesia, -72

Soda with a trace of potash, -43

Loss on ignition, -IB

Oxygen.

6260 33 38

.... 5-78
.... 2-82
.... 4-03

-29

.... 11

99-71

The oxygen of the protoxyds and peroxyds in the above
analysis equals 443 and 8-60, If to these we add the silica
corresponding to 13-00 of oxygen, we shall have 61-33 parts of
epidote, leaving 32-22 parts of silica nncombined. The density
of the mass is that of a mixture of epidote and quartz in the
above proportions, and in some specimens where the rock be-
comes granular, the two species are easily distinguishable. {Geol.
Survey of Canada, Report, 1858). This epidote rock then is com-
pletely dist'uct from the saussurite of Orezza.

The two silicates zoisite and meionite offer a remarkable in-
stance of that isomerism in mineral species upon whose import-
ance I have long insisted. The relation of the specific gravity
to the empirical equivalent weights of minerals, must enter as
an essential element into a classification which shall unite
the chemical and natural-historical systems. Similar isomeric
relations exist between kyanite and sillimanite, rutile and ana-
tase, and as I have elsewhere endeavored to show, among the
carbon-spars. It becomes necessary in the study of mineral
species to determine their relative equivalent weights, to which
specific gravity must be the chief guide. — {Proc. Am. Assoc.
Adv. Science, 1854, pp. 240-247).*

* The action of heat upon organic bodies of high equivalent tends to resolve
them into simpler and less dense i-orms, (wc except of course the simultaneous pro-
ductions of small portions of more complex hydrocarbons). Similar results are
obtained when the denser silicates are fused. Tims according to Magnus the specific
gravity of garnet is lessened ouc-fifth by fusion, while that of id;)Crase is reduced
from 8'34 to 2'94. Epidote by ignition has its density changed from 3'40 to 3 '20
according to Ramraelsberg, and saussurite is converted by fusion into a soft glass of
specific gravity 2'8. The silicates thus moditied are decomposable by acids like the
basic feldspars ; idocrase and garnet crystallize after fusion, the hitter according to
von Kobell in octahedrons. !).?ville found the density of Imrnblende and pyroxene to
be reduced by fusion fronk b'2 to 2'8, orthoclasa from 256 to 235, and labradorito
from 2689 to 2-525.

14 T. S. Hunt on Euphotide and Saussurite.

7. Srmragdiie.— The smaragdite or diallage of the eupliotides
appears to have been first examined by Vauquelin, who found
in a specimen from Corsica with specific gravity 3'0 ; silica 50*0,
alumina 210, Ihne 13-0, magnesia 6-0, oxyd of iron 5*5, oxyd of
chroniium 7-5, oxyd of copper 1-5 =104-5. (Beudant, Mineralo-
gie, 11, p. 134). Boulanger subsequently analvzed the diallage
from the euphotide of the Fiumalto already described. It had
a density of 3-10, and gave silica 40'8, alumina 12-6, lime 23-0,
magnesia 11-2, protoxyd of iron 3-2, protoxyd of manganese 1*4
oxyd of chromium 2-0, water 5 '2 =99 -4.— Mm?, des Mines, \3]
viii, 159).

I have analyzed the grass-green smaragdite already described
as occurring in masses an inch in diameter imbedded in the
saussurite VI. It was to some extent penetrated by the latter
mineral, and contained irregularly disseminated slender prisms
of hornblende, apparently associated with talc. The analysis
gave as follows :

?'l'ca, ., 64-30

Alumina 4.54

S™^-. '.'.".*. 18-72

Magnesia, Ig.Ql

rrotoxyd of iron, g.gij

Oxyd of chromium, * .gj

Oxyd of nickel, '..'..'.*.'.*.' .■.■;.';.' traces

?°^^ ••.•••• 2-80

Loss by igmtion, .gQ

9915

A partial analysis of another specimen gave alumina 8*80
hme 14-22, magnesia 18-07, protoxyd of iron 2-34. The pale
green color of the powdered smaragdite becomes brownish on
Ignition. The small portion of nickel, whose presence I have
already shown in a great number of chromiferous serpentines
and diallages,* gave evidence of a trace of cobalt before the
blowpipe. The oxygen ratios of the silica, alumina and pro-
toxyds in the above analysis are as 28-96 : 2-12 : 13*29 Its com-
position is evidently that of a pyroxene, with some admixture
of saussurite and probably of talc. A portion of the latter
mineral from one of the euphotides of Mt. Rose, was submitted
to analysis, and allowing for a small admixture of saussurite was
found to have the composition of ordinarj talc, being a hydrated
silicate of magnesia with a little iron and a trace of nickel

Co7icluswns.—l. The true euphotide is distinct from the dial-
lagic dolerites, with which most modern lithologists have con-
founded it, and which are composed of pyroxene and a feldspar
having the constitution of andesine, labradorite, or a still mere
basic variety approaching to anorthite. By the substitution of
hornblende tor pyroxene these dolerites pa«a into diorite or
diabase.

* This Journal, [2,] xxri, 237.

T. S. Hunt on Euphotide and Saussurite. 15

2. The euphotides of Mt. Kose according to my observations
are composed of sraaragdite (a pyroxene containing chrome and
nickel ) m a base of saussurite, which is a compact zoisite. or
lune-alumina epidote, containing portions of magnesia and soda
and havmg a hardness of 7-0 and a specific gravity of 3-38^
6 68 ; characters which at once distinguish it from the feldspars.
1 hese euphotides also contain as accidental minerals, talc, actino-
labradOTite^^^^'^'' ^ vitreous cleavable feldspar resembling

3. While the minerals analyzed as saussurite by Stromever
and Delesse are feldspars, that from Mt. Gen^vre examined bv
iSoulanger has the composition and specific gravity of meionite
a species which is isomeric with zoisite; the saussurite from
Orezza according to the same observer has a like composition
but a density intermediate between these species. The saussu-
rite examined by Thompson is apparently a peti-osilex.

4. ±Jy its great density and its composition, the euphotide of
Mt. Rose is related to certain rocks in which a white Lrnet re-
sembling saussurite, is mixed with serpentine, with hornbleide,
tni Tt *./el^spatbc mineral. These aggregates associated
with ophiohtes, albitic diorites, and a rock male up of epidote
and quartz, occur m the form of beds in the crystalline schists of
the altered Silurian series in Canada.*

217. S xLHTst'''''^' '" '^' ^''^""^ "^ Ophiolite», this Journal, [2J. vol.

XXT,