A Text-book of Mineralogy: With an Extended Treatise on Crystallography and Physical Mineralogy

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J. Wiley & sons, Incorporated, 1922 - Crystallography - 720 pages
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Page 158 - A small boy employed underground to push trams along a twin way. (Gresley) .Twin crystals. Crystals in which one or more parts, regularly arranged, are in reverse position with reference to the other part or parts. They often appear externally to consist of two or more crystals symmetrically united, and sometimes have the form of a cross or star.
Page 646 - On distillation it affords, after drying, 40 to 66 per cent. of volatile matter, and the material volatilized includes a large proportion of burning and lubricating oils, much larger than the above kinds of bituminous coal; whence it is extensively used for the manufacture of such oils. It graduates into oil-producing coaly shales, the more compact of which it much resembles.
Page 404 - A velvet-black siliceous stone or flinty jasper, used on account of its hardness and black color for trying the purity of the precious metals. The color left on the stone after rubbing the metal across it indicates to the experienced eye the amount of alloy.
Page 454 - Color white or pale shades of yellow, red or green, less commonly dark. 6, In composition silicates of aluminium with either potassium, sodium, or calcium, and rarely barium, while magnesium and iron are always absent.
Page 646 - Pennsylvania has a specific gravity of 1.26 to 1.37; of Newcastle, England, 1.27; of Scotland, 1.27 to. 1.32; of France, 1.2 to 1.33; of Belgium, 1.27 to 1.3. The most prominent kinds are the following: 1374. 3. Caking Coal. — A bituminous coal which softens and becomes pasty, or semi-viscid, in the fire. This softening takes place at the temperature of incipient decomposition, and is attended with the escape of bubbles of gas. On increasing the heat, the volatile products, which result from the...
Page 344 - The upper portion of the deposit consists of a friable mass of pale yellow color, called the "yellow ground." Below the reach of atmospheric influences the rock is more firm and of a bluish green color; it is called the "blue ground." This consists essentially of a serpentinous breccia inclosing fragments of carbonaceous shale, bronzite, diallage, garnet, magnetite, etc. The diamonds are rather abundantly distributed through the mass, often to the amount of four to six to the cubic yard. These...
Page 486 - In part a normal metaslllcate of calcium and magnesium, RSiOi, usually with iron, also manganese, and thus in general analogous to the pyroxenes. The alkali metals, sodium and potassium, also present, and more commonly so than with pyroxene. (Dana). The name of the mineral is prefixed to many rock names. Hornblende schist.
Page xi - ... exhibited in its crystalline form and other physical properties. A mineral must be a homogeneous substance, even when minutely examined by the microscope; further, it must have a definite chemical composition capable of being expressed by a chemical formula.
Page 189 - HARDNESS. The hardness of a mineral is measured by the resistance which a smooth surface offers to abrasion. The degree of hardness is determined by observing the comparative ease or difficulty with which one mineral is scratched by another, or by the finger nail, or by the knife or file.
Page 402 - Luster vitreous."sometimes greasy; splendent to nearly dull. Colorless when pure; often various shades of yellow, red, brown, green, blue, black.

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