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

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Wiley, 1877 - Crystallography - 485 pages
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Page 86 - 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 393 - 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 117 - THE specific gravity of a mineral, is its weight compared with that of another substance of equal volume, whose gravity is taken at unity.
Page 419 - ... ordinary landscape perspective. If parallel lines were drawn from the vertices of the solid angles of a Crystal, to a board placed behind it, and the points thus formed on the board were connected by straight lines, as in...
Page 169 - Sodium Strontium . Sulphur . Tantalum . Tellurium . Thallium . Thorium . Tin Titanium *. Tungsten . Uranium . Vanadium Yttrium . Zinc Zirconium...
Page 392 - The fluid kinds change into the solid by the loss of a vaporizable portion on exposure, and also by a process of oxidation which consists first in a loss of hydrogen and finally in the oxygénation of a portion of the mass.
Page 115 - ... galena. Sectile, when pieces may be cut off with a knife without falling to powder, but the substance still goes to pieces under the hammer. This is really a condition intermediate between brittle and malleable. Malleable, when the substance can be beaten out under the hammer without flying to pieces, like gold. Ductile, when the substance can be extended or drawn out by tension, as in...
Page 394 - ... appearance of a banded structure; and it breaks with a conchoidal fracture and smooth surfaces; color, dull black or grayish-black. 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...
Page 59 - I. The sine of the middle part is equal to the product of the tangents of the adjacent parts. II. The sine of the middle part is equal to the product of the cosines of the opposite parts.

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