Beryllium, 10 Bezils, 66 Black stones, list of, 79 Blue sapphire, composition of the, 10 stones, list of, 77 Bone-turquoise, 106 Break, as opposed to cleavage, 19 Brilliant-cut stones, 66 Brown stones, list of, 76 Building up of crystals, 13 Burnt, or pinked topaz, 92 Cabochon-cut stones, 64 (the double), 65 (the hollow), 65 Carbonate series, 11 Carbuncle, 102, 103 Cat of Egypt, 89 Cat's eye stones, 82, 87-91 list of (see "Chatoyant Stones"), 78 Ceylonese cat's eye (see "Cat's eye") Change of colour (not to be confused with "Play of colour" and "Opalescence," which see; see also "Fire"), 36 Characteristics of precious stones, 1, 3 Chatoyant stones, list of, 78 Chemical illustration of formation of precious stones, 8 Chloride of palladium in dichroscope, 34 Chrysoberyl, 88 Chrysolite, 11 ordinary, or "noble", 85 oriental, 85 Cinnamon stone, 102 Claims of precious stones, 4 Cleavage affecting tests, 43 and "cleavage" as opposed to "break", 19, 22 Colour, 26, 28, 30, 32 Colourless stones, list of, 75 Colours and characteristics of the various opals, 35, 36 of precious stones, list of, 75-79 Common garnet, 101 opal, 35 Composite crystals, 13 Composition of paste, or strass, for imitation stones, 71 Composition of precious stones, 7 Converted stones, 72 Corundum, 82 Crown portion of stones, 65, 66 Crystalline structure, physical properties, of 13 Crystallography, 14 Crystals, axes of symmetry, 15 groups of, 15, 16 planes of symmetry, 15 systems of, 16 (1) Cubic--isometric, monometric, regular, 16 (2) Hexagonal--rhombohedral, 16 (3) Tetragonal--quadratic, square prismatic, dimetric, pyramidal, 16 (4) Rhombic--orthorhombic, prismatic, trimetric, 16 (5) Monoclinic--clinorhombic, monosymmetric, oblique, 16, 17 (6) Triclinic--anorthic, asymmetric, 16, 17 treatment of, 14 Culasse portion of stones, 66 Cullinan diamond (see also "Stars of Africa"), 22, 64, 68, 80 Cutting of precious stones, 3, 4, 62 Cymophane, 90 Definition of a precious stone, 1 Diamond, characteristics of the, 80 composition of the, 10 (sapphire), 86 unique, 10 (zircon), 99 Diaphaneity, 26, 28 Diaphanous stones, 28 Dichroscope, 33 how to make a, 33 how to use a, 34 Dimorphism in precious stones, 25 Double cabochon-cut stones, 65 refraction (see "Refraction") Doublets, 72 Electric and magnetic influences, 57 experiments with precious stones and pithball and electroscope, 57 experiments with tourmaline, 58, 59 Emerald, 10, 11, 95, 96 oriental, 85 En cabochon-cut stones, 64 Experiments to show electric polarity, 58, 59 Facets in stones, description of the, 67, 68 Feminine stones, 85 Fire in stones (see also "Change of Colour," "Opalescence," and "Play of Colour"), 36, 37 Fire opal, 35 Flame-coloured stones, list of, 76 Flaws, 63 Formation of precious stones, 5, 8 chemical illustration of, 8, 9 Garnet, 11, 100