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acid aggregates albite alumina andesites anorthite antimony aragonite augite basal plane botryoidal brachy-dome brachy-pinacoid calcite cent Chatoyancy chemical composition chloride cleavage clino-pinacoid colour colourless combination compounds constituting contains copper crust crystalline crystals cube decomposition deposits deutero-pyramid dolomite faces felspar fibrous forms formula fracture galena gem-stones gems gold granite granular green grey gypsum hardness hemihedral hemimorphic Hexagonal system hornblende hydrated silicate igneous rocks intercepts iron iron-pyrites isomorphous lateral axes lime lustre macro-dome macro-pinacoid magnesia manganese masses metal mica Monoclinic Monoclinic system nodular occurs massive octahedron olivine opaque ortho-pinacoid orthoclase oxide oxygen parallel pinacoids plagioclase planes of symmetry platinum potash prism prismatic pyramid pyrites quartz Regular system rhombic dodecahedron Rhombic system rhombohedral right angles rock-forming minerals salts silicate silver six-sided soda soluble in water specific gravity striation sulphates sulphide sulphur surface tabular tion transparent Triclinic twinned unit distance usually varieties veins veinstone vertical axis vitreous yellow zinc
Popular passages
Page 31 - The specific gravity of a body is the ratio of the weight of the body to the weight of an equal volume of some other body taken as the standard of comparison, and whose specific gravity, therefore, is taken as the unit.
Page 32 - The weight of a body in water is less than its weight in air by an amount equal to the weight, of an equal volume of water. 15. The Specific Gravity of a substance is the ratio of its weight to that of an equal volume of water. The specific gravity is found by weighing a body in air and then in water. The difference is the weight of an equal volume of water. Then if "W equals weight in air; and W equals weight in water, then W "W' = weight of water displaced, and W Specific gravity = w_w> (l8) as...
Page 34 - ... employed in cutting, does not wear away the edge of the tool. By hardness is understood the resistance offered by a body to the separation of its particles. The hardness of a mineral is measured by the force required to scratch it with a steel point or pointed fragments of certain standard minerals. The results obtained from one and the same mineral are found to vary slightly with the crystalline face experimented upon, and even with the direction on one and the same face.
Page 24 - Those forms in any crystal system which show the full number of faces required by the symmetry of the system are called holohedral forms.
Page 89 - O3 and is composed of 56. per cent of lime and 44. per cent of carbon dioxide or carbonic acid.
Page 8 - ... at right angles to one another, and at right angles to the direction of propagation of the energy.
Page 34 - The minerals in this scale beginning with the softest mineral, are : — 1. talc, 2. gypsum, 3. calcite, 4. fluorspar, 5. apatite, 6. felspar, 7. quartz, 8. topaz, 9. corundum and 10.
Page 5 - ... of symmetry, and there must also be faces corresponding to these on the opposite sides of the planes of symmetry, and making equal angles with them respectively. A group of faces which are mutually related in accordance with this law is technically described as a form.
Page 8 - It is contained by six equal squares, each of which cuts one axis at right angles, and runs parallel to the other two, thus coinciding with the three chief planes of symmetry of this system.
Page 5 - SYMMETRY. metry, may be termed an axis of symmetry. The fundamental law which underlies crystallography is the law of symmetry. It may be formulated thus : Every face of a crystal must possess a corresponding face parallel to it FIG.