THE CANADIAN JOURNAL. NEW SERIES. No. LXX. NOVEMBER, 1869. ANALYSES OF SOME CANADIAN MINERALS. BY E. J. CHAPMAN, PH. D. PROFESSOR OF MINERALOGY AND GEOLOGY IN UNIVERSITY COLLEGE, TORONTO. 1. Graphite from the township of Buckingham, on the Ottawa, (lot 19, range 5). The sample employed in this analysis was apparently very pure: soft, black, sub-foliated, and highly lustrous. Sp. gr. 2.265. The moisture was determined by desiccation in an air-bath at a temperature of 212°. The carbon was then burnt off by prolonged ignition in the muffle of an assay-furnace; and the resulting ash was fused with carbonate of soda in a platinum vessel, and decomposed in the usual way by chlorhydric acid. 6314 grammes lost 82 milligrammes by complete desiccation, and left 1.1731 gramme of very faintly coloured ash after exposure to long continued ignition. The analysis thus yielded : Carbon ...... 80.12 = Another sample (sp. gr. 2-272) yielded: moisture 1.14, ash 22.06, carbon (by difference, as before) 76-80. The composition of the ash was not determined. 2. Silver Glance: from Thunder Bay, Lake Superior. The sample consisted of a small mass of distorted crystals (combinations of cube and octahedron), perfectly sectile and malleable. Sp. gr. 7.31. Decomposition was effected by nitric acid; the silver weighed as Ag Cl; and the sulphur partly as S, and partly as Ba SO4. The analysis of 1-933 gramme yielded in per centage values : Sulphur ....... ..... 13.37 86.44 3. Magnetic Pyrites: from Madoc (lot 18, con. 2). Some carefully selected fragments, apparently quite free from FeS2, were taken for the analysis, and decomposed by chlorhydric acid with subsequent addition of nitric acid. They were strongly magnetic, and the mass from which they were separated exhibited well marked magnetic polarity. Their sp. gr. was equal to 4-485; but most examples from this locality, in consequence of intermixed silica or siliceous rockmatter, vary, as regards sp. gr., from about 4-2 to 4 3. The sample contained no trace of either nickel or cobalt. An assay of 50 grammes, for gold, left nothing on the cupel. In another examination, the sulphur was determined by decomposing a portion of the finely powdered mineral with nitre and carb. soda in a porcelain crucible. 1.155 gramme gave 3.377 grammes of Ba SO. This is equivalent to 40-17 per cent. of sulphur. 4. Arsenical Pyrites: from Tudor, in Hastings county. This sample, if I may so call it, was not analysed, as it consisted merely of a few minute but well-defined crystals, given to me some time ago by my colleague, Professor Croft. Two of these little crystals, examined by the blowpipe, shewed unmistakably the re-action of cobalt; and the presence of this metal appears to be connected with a crystallographic peculiarity in these and other crystals of mispickel. The more common crystals of this mineral, consist, it is well known, of a rhombic prism combined with the planes of a side-polar or brachydome. In these Tudor crystals, the brachydome in question is replaced by two of less obtuse type, namely, and . Now, the form, the summit angle of which equals 118° 30', is a comparatively rare form, but it appears to be always present in the cobaltiferous varietics of mispickel, and in the allied species glaucodot. 5. Arsenical Pyrites: from Marmora. Assays of several samples of coarsely crystalline mispickel from this locality, have yielded me comparatively large amounts of gold. In some specimens "free gold" is present in visible specks and grains, but from samples in which no trace of gold could be perceived under the magnifying glass, I have obtained returns varying from 1 oz. 3 dwts. 8 grs. to 3 oz. 8 dwts. 20 grs. in the ton of 2,000 lbs. of ore. 6. Prehnite from Slate River, Lake Superior. : The specimen analysed was obtained personally, in the summer of 1868, from Slate River, a rocky stream which enters the Kaministiquia about fourteen miles above the mouths of the latter on Thunder Bay. The specimen formed part of a narrow vein of more or less compact Prehnite, which cuts at that place the high cliffs of dark alum-bearing slate, or shale, forming the sides of the ravine through which the river flows. These slates belong to the lower portion of Sir William Logan's "Upper Copper-bearing Series of Lake Superior." Near the Prehnite. vein, a very remarkable dyke of dark grey Trap or Dolerite crosses the river. The stream has cut its way through it, and as the cliffs at that spot have been much wasted by atmospheric action, the dyke stands out like a wall, varying from about ten to thirty feet in height, with a width of about three feet. On the right bank also, where it retains its wall-like aspect to the edge of the stream, it has been hollowed out into an arch through which a man might pass without stooping. The Prehnite was only partially (or at least, very slowly) attacked by chlorhydric acid. It was therefore decomposed by previous fusion with carb. soda, the water being of course determined separately. Sp. gr. 2.882. |