An Elementary Introduction to Mineralogy

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Longman, Brown, Green, and Longmans, 1852 - 700 pages
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Page 53 - It may also be defined as the sine of the angle of incidence divided by the sine of the angle of refraction, as light passes from air into the substance.
Page 9 - holohedral forms- of any system are those which possess the highest degree of symmetry of which the system admits. ' Hemihedral forms- are those which may be derived from a holohedral form by supposing half of the faces of the latter omitted according to a certain law.
Page 277 - There are several instances of this pseudomorphism occurring at foreign localities ; for instance, at Munzig, at Fahlun, and at Herzogau. Chiastolite, according to Brooke and Miller, " appears to be a variety of Andalusite having prisms of a darker substance in the centre, and sometimes in each angle, connected by thin plates of the same. The dark portions are either the slate, in which the crystals are imbedded, or discolorations produced by carbonaceous matter, which disappear on igniting the crystal.
Page 64 - The Specific Gravity of a substance is the ratio of its weight to that of an equal volume of water.
Page 550 - Pyr., etc. — BB on charcoal easily reduced. Partially soluble, with a slight effervescence, in nitric acid, leaving a residue of sulphate of lead (Brooke). Obs. — Occurs at Leadhills, Scotland, accompanying other ores of lead, in crystals with linnrit : at Ked Gill in Cumberland ; also at Retzbauya in Hungary ; Tanné in the Harz.
Page 45 - A twin-crystal is composed of two crystals joined together in such a manner " that one would come into the position of the other by revolving through two right " angles round an axis which is perpendicular to a plane which either is, or may be, " a face of either crystal. The axis will be called the twin-axis, and the plane to " which it is perpendicular the twin-plane." Miller's Treatiie on Crystallography, p. 103. In the text the word
Page 9 - ... indices and also the new parameters when referred to any other axes originating in the same point." This problem is solved in the paper, but the solution is too long to be here given. For the purposes of this paper only a particular case of the general problem is required. For in the rhombohedral system the axes make equal angles with each other, and the parameters are equal. Let eo be the angle between the rhombohedral axes, and a the magnitude of each of the equal parameters.
Page 70 - Aluminum Al Antimony Sb Argon A Arsenic As Barium Ba Beryllium Be Bismuth Bi Boron B Bromine Br Cadmium Cd Calcium Ca Carbon C Cerium Ce Cesium Cs Chlorine Cl Chromium Cr Cobalt.. Co Columbium...
Page 341 - ... direction of the normal to c. Cleavage ; m, v and w fair, r indistinct and interrupted, traces along p and y. Fracture ; conchoidal to uneven. Brittle. Transparent to translucent on the edges. Lustre ; highly vitreous. Colour ; clove-brown of various shades, inclining to plum-blue to pearl grey. It exhibits trichroism. On looking through a crystal in the direction of either optic axis, a dark violet stripe is seen, interrupted at the point occupied by the axis (Miller).
Page 63 - Calcite. 4. Fluorspar. 5. Apatite. 6. Felspar. 7. Quartz. 8. Topaz. 9. Corundum. 10. Diamond.

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