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 ^OVA SCOTJ4 
 
 PROVINCE HOUSE 
 
M-ir 
 
 ON THE GEOLOGICAL RELATIONS OF THE IRON 
 ORES OF NOVA SCOTIA. 
 
 (^Read before the American Association for the Advancement 
 
 of Science.) 
 
 By J. W. Dawson, LL.D., F.R.S. 
 
 The Iron Ores of Nova Scotia, long neglected, have recently 
 begun to attract the attention of capitalists to an extent in some 
 degree commensurate with their importance. The magnitude 
 and variety of the deposits, the great richness of the ores, their 
 proximity to the Atlantic and to great deposits of coal, are all 
 features which give them very great economic value, and must 
 eventually cause them to take no small part in contributing to 
 the iron supply of the world. My purpose in the present paper 
 is, with the aid of recent researches in which I have been occu- 
 pied, to give a concise summary of the geological position and 
 mode of occurrence of the principal deposits, and more especially 
 of those facts which have been developed since the publication of 
 my ** Acadian Geology." 
 
 If we arrange these deposits in the first place under the two 
 heads of Beds conformable to the stratification and Veins, we 
 Bhall find that the former occupy three distinct geological hori- 
 Bons — that of the Lower Helderberg or Ludlow in the upper 
 part of the Silurian, that of the Oriskany at the base of the De- 
 vonian, and that of the Lower and Middle Carboniferous. The 
 latter occur in altered rocks which may be assumed to be of 
 
J^l 
 
 
 Silurian age, in the Lower Carboniferous, and at the junction of 
 these two groupr of rocks. We may shortly consider the deposits 
 of these eeveral kinds and ages in their order. 
 
 1. Bedded Ores. 
 
 (1) Great Hematite Bed of the Lower Helderherg Series. 
 
 This, in so far as at present known, is most extensively de- 
 veloped in the vicinity of the East Branch of the East River of 
 Pictou, and on the upper part of Sutherland's River. Here the 
 rocks which rise unconformably from beneath the Carboniferous 
 beds of the Pictou coal-fie'id, consist in great part of gray and 
 olive BJates, usually coarse and unevenly bedded, and with 
 occasional calcareous bands, holding the characteristic fossils of 
 the " Arisaig group," a series in Nova Scotia equivalent to the 
 Lower Helderberg of American geologists, though in its specific 
 forms more nearly allied to the English Ludlow than to groups 
 of this age on the great inland plateau of America. These beds 
 are affected with slaty cleavages, highly inclined, much faulted, 
 and folded in abrupt anticlinals, po that their detailed arrange- 
 ment has not yet been satisfactorily traced. The great ore-baud 
 which forms one of the most conspicuous marks lor unravelling 
 their complexities, has been traced mainly along two distinct 
 lines of outcrop, both somewhat curved and broken, and which 
 seem to lie on the opposite sides of an anticlinal axis. It has 
 also been recognized in two other localities where it must come 
 up on distinct lines of outcrop, the precise relation of which to 
 the others has not yet been ascertained. 
 
 The ore bed ia accompanied .y a thick band of olivaceous 
 slates, and beneath this there appears hard ferruginous quartzite 
 which Dr. Honeyman compares to the Medina sandstone. Lower 
 than this and possibly unconformable to it are black and green- 
 ish slates with bands of quartzite and soft chloritic and nacreous 
 schists which as yet have afforded no fossils. They are associated 
 with hard beds or masses of rock rising into some of the highest 
 eminences, and which have usually been described as trap, but 
 which seem to consist for the most part of an indurated slaty 
 breccia or conglomerate, corresponding very nearly in character 
 to the typical graywacke of the older German geologists. These 
 rocks may be of middle Silurian age, though possibly in part 
 older, and we shall meet with them again in connection with the 
 great vein of specular iron. 
 
',^:^«*- 
 
 i 
 
 The ore-bed where most largely developed attains a thickness 
 of about thirty feet, and in places where it has been opened up 
 by exploratory works, it has been found to aflford from ten to 
 twenty feet in thickness of good ore. This ore is a red hematite, 
 sometimes compact and laminated, but more frequently of an 
 oolitic character occasioned by tiie arrangement of the peroxide 
 of iron in minute concretions enveloping grains of sand. By the 
 increase of these silicious grains it passes in the poorer portions 
 into a sort of ferruginous sandstone. Similar beds of fo3siliferous 
 ore are well known to occur in the Clinton group of New York 
 and Pennsylvania, and Pro! Hall informs me that they are 
 found also iu the Lower Helderberg series of New York. 
 
 Along the different lines of outcrop above referred to, this bed 
 has been traced for several miles, and being of a hard and resist- 
 ing character, it rises into some of the higher eievations of the 
 country. Though not one of the richest ores of the district, its 
 great quantity and accessibility render it highly important for 
 practical purposes. The analyses made of it show a perjentage 
 of metal varying from 43 to 54 per cent. The foreign matter is 
 principally Silica, and the proportions of Phosphorus and Sulphur 
 are small — one of the specimens analyzed affording none whatever, 
 another .22 Phosphoric Acid and .29 Sulphur. These analyses 
 were made at the instance of Mr. E. A. Prentice, now organizinsr 
 a company to work this and other deposits in the district. The 
 principal exposures of this bed are distant only twelve miles from 
 the great collieries of the East River of Pictou, and less than 
 ten miles from the Pictou and Halifax Railway. This deposit 
 was first described by Mr. R. Browu in Haliburton's History of 
 Nova Scotia, 1829, and subsequently by the writer in Acadian 
 Geology. More recently exploratory works have been carried on 
 and a practical report made by Mr. G. M. Dawson, Associate 
 of the School of Mines, London ; and the bed has been traced and 
 collections of its fossils made by Mr. D. Fraser of Springville. 
 
 (2) Hematite and Magmtic Iron of Nictaxix and Moose River. 
 
 This deposit takes us to the other extremity of Nova Scotia, 
 and brings us a stage higher in geological time, or t( he period 
 of the Oriskany Sandstone. It would indeed appear that the 
 conditions of ore-deposit so marked in Eastern Nova Scotia in 
 the upper Silurian, were continued in the western part of the 
 Province into the Devonian. In many specimens of the Nictaux 
 
jW"^ 
 
 ■^■p 
 
 m 
 
 ore the chief apparent difference as compared with that of Pictou 
 is in the contained species of fossils. 
 
 Where I have examined this bed, it appears to be six teet thick 
 and enclosed in slaty rocks not dissimilar from those associated 
 with the Silurian ore of Pictou. Recent explorations at Nictaux 
 are said to have developed extensions of this deposit ; but I have 
 no details of these. As rocks of the Arisaig group are known to 
 inderlie the Nictaux beds, it is not impossible that additional 
 beds of ore may be found in these. The normal condition of 
 the iron of the Nictaux bed is that of peroxide; but localjv it 
 has lost a portion of its oxygen and has become magnetic. 
 This T believe to be a consequence of local metamorphism con- 
 nected with the immense granite dikes which traverse the Devon- 
 ian rocks of this region. 
 
 The Nictaux ore is more highly fossiliferous than that of 
 Pictou, and contains a larger proportion of Phosphate of Lime. 
 Tn the attempts hitherto made to work this ore the distance 
 from coal has been a main disadvantage, but the construction of 
 the Windsor and Annapolis railway has diminished this. The 
 Devonian beds holding this bed are described in "Acadian Geol- 
 ogy." An analysis of a specimen made many years ago gave 55 
 per cent of iron. 
 
 (3) Bedded Ores of the Carhoni/erous System. 
 
 The most remarkable of these is a bed of crystalline Spathic 
 iron or Siderite, occurring in the Lower Carboniferous series, 
 near Sutherland's River in the County of Picton. As described 
 by Mr. G. M. Dawson, who prosecuted works of exploration in 
 it last year, it is a conformable bed, occurring in the Lower Car- 
 boniferous red sandstones, and varying from six feet six inches to 
 ten feet six inches in thickness. It is accompanied with smaller 
 bands of the same mineral, and at no great vertical distance from 
 it is a bed of gypsum. Its mode of occurrence is on the whole 
 not dissimilar from that of the uon fossiliferour sub-crystalline 
 limestones which occur in some parts of the Lower Carboniferous 
 series associated with the gypsum. This ore is a true Spathic 
 Iron, granular and crystalline in texture, and when unweathered 
 of a light gray colour. It affords from 42 to 43 per cent, of 
 iron and contains from 2 to 8 per cent, of manganese. This bed 
 is only four miles distant from the "Vale" colliery, and is in- 
 tended to be worked in association with the Hematite already 
 
■ 
 
 described, aud with the other ores on the East River of Pictou 
 possessed by the sam-j proprietors. From the Report of Mr. 
 Andrews on the second geological district of Ohio, it would ap- 
 pear that similar beds, though on a smaller scale, occur in the 
 Lower Carboniferous series of that Stat?. In Nova Scotia this 
 bed is at present altogether unique. 
 
 Clay Ironstones occur in many parts of the Nova Scotia coal- 
 field. In the workings of the main seam of the Albion Mines, 
 Pictou, considerable quantities of nodular black ironstone are 
 extracted, and will, no doubt, be utilized. In the beds under the 
 main seam there are also chiys rich in ironstone concretions. 
 Beds with ironstone balls also occur in the measures north of the 
 New Glasgow conglomerate, and one of these is remarkable for 
 the fact that the nodules were found by Dr. Harrington to contain 
 nuclei of Blende, a mineral otherwise unknown in the carbonife- 
 rouif of Nova Scotia. No attention has yet been given to these 
 ons as sources of 'ron, but it may be anticipated that a demand 
 for them will urise in connection with the richer ores in the 
 alder formtHono. 
 
 II. Veins op Iron Ore. 
 
 ^1) Gn-at &j}ecidar Iron Veivs of the Siluri'tn States and 
 
 Quartzites. 
 
 In a paper on the metaniorphic and metalliferous rocks of 
 Eastern Nova Scotia in 1848,* I mentioned the fact that the in- 
 land series of metamorphic rocks (bounding the coast series now 
 known as the gold-bearing series) and believed to be of Upper or 
 Middle Silurian age, abound in veins of specular iron, associated 
 with spathic iron and ferruginous dolomite, and occasionally with 
 metallic sulphides, and I described some of these deposits. In 
 the country eastward of Lochaber Lake, wheie this same forma- 
 tion occurs, not only are numerous small veins of specular iron 
 and carbonate of iron found in it, but a rich vein of Copper 
 Pyrites, noticed in " Acadian Geology," has recently been opened 
 up and found to be very valuable. 
 
 In most parts of the region these iron veins, though very 
 numerous, are of trifling thickness; but in two localities they 
 are known to attain to gigantic dimensions, rendering them of 
 great economic importance. 
 
 • Journal of Geological Society of London. 
 
«■ 
 
 The earliest known of these was the great vein of the Acadia 
 mine in the Cobcquid mountains, discovered by the late Mr. G. 
 Duncan, and on which I reported in 1845. These hills consist 
 on their southern side of parallel bands of olive and black slato 
 with beds of quartzite, all very highly inclined. The iron vein 
 is a great irregular fissure, extending for many miles parallel to 
 the bedding, and apparently accompanying a band of quartzite. 
 It contains in addition to crystalline and often micaceous Specu- 
 lar iron and Magnetic iron, large quantities of a rich earthy red 
 ore, which from the crystalline pianos which it presents, would 
 seem to have been a Carbonate of Iron decomposed and oxidised. 
 These iron ores are associated with large quantities of a crystal- 
 line ferruginous Dolomite, allied in composition to Ankerite. 
 This may be regarded as the veinstone to which the i''on ores 
 are subordinate, and which in the thinner parts of the vein occu- 
 pies nearly its whole breadth. At the outcrop of the vein it is 
 in some places weathered to a groat depth into a soft and very 
 pure yellow ochre. Small quantities of sulphides of iron and 
 copper and of sulpliate of barium are occasionally present. In 
 additioi. to the above, which may be regarded as the primary 
 contents of the vein, there occur in some parts of it socuudaiy 
 deposits of concretionary Limonite, which have of late years 
 afforded a very large part of the ore smelted by the Acadia 
 Company. 
 
 In some places the thickness of this vein has been found to 
 be 150 feet, with intercalated masses of rock, but it is very irregu- 
 lar, diminishing occasionally to mere strings of ankerite. It is 
 remarkable th;it in the Cobcquid mountains, which are cut by 
 transverse ravines to the depth of about 300 feet, the vein does 
 not appear to be well developed in the bottom of the ravines, but 
 only in the intervening heights At first I was disposed to ac- 
 count for this by supposing that the deposit is '.vpdge- shaped, 
 diminishing downward ; but I have more recently been inclined 
 to believe that the large development of the vein is dependent on 
 differences in the containing rocks which have rendered them 
 harder and more resisting at the points of such greater develop- 
 ments. 
 
 With respect to the age of these beds, they must be elder than 
 the Lower Helderberg rocks, which both at the eastern end of 
 the Cobequids and at the East River of Pictou, rest upon them. 
 They are on the other hand probably newer than the auriferous pri- 
 
..«&£ 
 
 mordial rocks of the Atlantic coast. As they have afforded no 
 fossils their age doe? not at present seem capable of more precise 
 definition. With regard to the filling of the vein fissures, this, 
 if coeval with the metamorphism of the containing beds or im- 
 mediately subsequent thereto, would fall between the period of 
 the lower Devonian and that of the lower Carboniferous, or 
 within the Devonian age. The denudation connected with the 
 Lower Carboniferous conglomerates and the fragments contained 
 in these conglomerates, seem to imply that the ore-bearing slates 
 were then in the same condition as at present. On the other 
 hand the Lower Carboniferous sandstones themselves contain iu 
 places narrow veins of specular iron, which also occurs, as well 
 as magnetic iron, iu the fissures of the Triassic trap. 
 
 On the west side of the East River of Pictou, there occur rocks 
 precisely similar to those of the Cobequid range, of which indeed 
 they may be regarded as an Eastern continuation, and including 
 an iron vein which must be regarded as the equivalent of that of 
 the Acadia Mine, which it resembles perfectly in mineral char- 
 acter and mode of occurrence, diff'ering only in the greater pro- 
 portionate prevalence of the specular ore.* 
 
 In New Lairg, a few miles from Glengarry Station, the most 
 western portion of this vein known to me, coctaius much Ankerite, 
 with strings of Specular iron ; and in large loose pieces there are 
 indications also of red ore whicli is not visible in place. Farther 
 to the eastward on the West Branch of the P]ast lliver of Pictou, 
 there appears a band of quartzite thirty feet thick filled with 
 veins of Limouite; but specular ore is not found at this place. 
 Still farther to the eastward and near the east branch of the 
 East lliver the specular vein attains a very large deve! .. -ment 
 shewing in some places a thickness of twenty feet of pure ore. 
 Its course is S. 60^ to 70" E. or nearly coincident with that of 
 the containir.g beds; and as on the Cobequids, its attitude is 
 nearly vertical and it appears to be tliickest and richest in the 
 rising grounds. In one very deep ravine the bed of quartzite 
 usually associated with the ore seemed to be wanting, and the 
 rein was represented by innumerable strings of Ankerite, forming 
 a network in the slate. As in the Cobequid vein, masses of Mag- 
 netic ore are occasionally mixed with the Specular. To complete 
 
 • This vein was first described by the late Mr. Hartley in the 
 Report of the (ieological Survey of Canada, 1870. 
 
the resemblance, loose masses of Limonite are found in the vicinity 
 of the /ein, giving riae to the expectation that a vein or veins of 
 this mineral may be found to be associated with the specular 
 ore. The ores of thia vein in Pictou CouLty are nearly pure 
 peroxide of iron, containing >om 64 to 69 per cent, of metal, 
 and can be obtained in great quantity from the outcrop of the 
 vein where it appears on tha rising grounds. 
 
 Mil, 
 
 a 
 
 Ideal Section, ihowing the general relation of the Iron Ores of the East 
 
 River of J'ictou. 
 
 1. Great bed of lleU Hi'iuatite. 
 
 2. Vf'in of Specular Iron. 
 
 3. Vein of Limonite. 
 
 («) Older Slate and Qiiartzite series, with Trap, &<:. 
 
 (A) Lower Helderberg formation and other Upper rfilurian rocks 
 
 (c) Lower Carboniferous of the East Branch of East River. 
 
 {^) Limonite verm of the East River of Pictou. 
 The valley of the East River of Pictou above Springville is 
 occupied by a narrow tongue of Lower Carboniferous rocks, 
 having at one side the slates containing the ore last mentioned,' 
 and on the other a more disturbed country already referred to 
 as containing the great Lower Helderberg bed of Hematite. It 
 is highly probable that the river valley follows .he line of an old 
 pre-carboniferous line of fracture, denuded and partially filled 
 with the Lower Carboniferous beds, including large deposits of 
 limestone and gypsum. At the line of junction of the Carbon- 
 iferous and older rocks on the east side of the river, occurs the 
 great Limouite vein of the district, forming a vein of contact of 
 exceeding richness and value. It fellows the sinuosities of the 
 margin of the older rocks, and varies in thickness and quality in 
 different places; being apparently richest opposite the softer 
 slates and where these are in contact with a black manganesian 
 limestone, which here, as in many other parts of Nova Scotia, 
 forms one of the lowest members of the Carboniferous series! 
 The ore is sometimes massive but more frequently in fibrous con- 
 cretionary balls of large size, associated with quantities of 
 
i3g»J 
 
 smaller concretionary or " gravel" ore. In some places the c-e 
 of iroi' is associated with concretions or crystalline raasses of 
 Pyrolusite and Manganite. 
 
 Denuding agencies in the Post-pliocene period have removed 
 portions of the vein and its wells, and have deeply covered the 
 surface in many places with debris. Hence the outcrop of the 
 vein was originally marked by a line of masses of the ore too 
 heavy to be removed by water. From the analogy of the other 
 veins to be mentioned in the .sequel, I was led to believe that the 
 source of these masses would be fouud in the Lower Carbonifer 
 ous rocks, and so stated tlie matter in the first edition of Aca<'ian 
 Geology (1855). Subsequentitr^ howe:er, the vein having been 
 exposed in situ, and one wall j ing to consist of mctamorphic 
 slate, it was described by Dr. iloneym.-.n and by Mr. Hartley of 
 the Geological Survey ^as a vein in the Silurian rocks. Still 
 more recently exploratory w ks conducted by Mr. G. M. D;'.w- 
 son. with the aid of Mr. D. Fraser, have clearly proved that the 
 vein follows the junction of the two formations. The ore of tK 
 vein is of the tinest quality, affording from 62 to 65 per cout. of 
 metallic iron. The more productive portions of this vein, as 
 well as of the specuh-r vein in its vicinity, are iu the hands of 
 the parties already referred to, in connection with the Hematite 
 bod. 
 
 (3) Limonite of Shuhenav<tdie, Old Barns and Broohfiel'' . 
 
 At the mouth of the Shubenacudie River, the lowest Carbon- 
 iferous bed seen is a dark-coloured laminated limestone, in all 
 probability the equivalent of the Manganesian limestone already 
 referred to, as well as of the Manganiferous limestone of Walton, 
 the Plumbiferous limestone ot the Stewiacke, and the lower 
 black limestone of Plaister Cove, Cape Breton.* This limestone 
 and the sandstones and maris overlying it, are traversed by large 
 fissure veins, holding a coi. fused aggregation of iron ores and 
 other minerals, as Limonite, Hematite, Gothite, Sulp;iate of 
 Barium, Calcite, &c., some of which appear sufficiently large and 
 rich for profitable exploration. In the same formations, further 
 to the ea.stward, at Old Bares, similar veins are found to be 
 largely developed, and at Brookfield, fifty miles east of the Shu- 
 benacudie, and apparently near the junction of the Low Car- 
 boniferous with older rocks, large surface masses of Limonite 
 
 * See Acadian Geology. 
 
10 
 
 appear to indicate an extensive deposit of similar nature, but 
 which has not, I believe, been yet so far opened up as to estab- 
 lish its practical importance. 
 
 (4) Iron Veins of the Triassic Trap. 
 Veins of Magnetite and Specular Iron occur in several locali- 
 ties in the great beds of trap associated with the Triassic red 
 sandstones of the Bay of Fundy, but so far as known these ores 
 are insignificant in quantity. 
 
 It will be observed from the above notes, that while the iron 
 vein of the Cobequid hills is at no great distance from the coal- 
 field of Cumberlaiid, with which it has now railway connection, 
 the still larger and more important deposits of Pictou are very 
 near to the extensive collieries of that district, and to railway and 
 water communication, so that every facility appears to exist for 
 their profitable exploration, and it may be anticipated that they 
 will soon be rendered available for the supply of iron of superior 
 quality, more especially to meet the large and increasing demand 
 of the Dominion of Canada.