INDEX

Adamantine lustre, 28 glimmering, 29 glinting, or glistening, 29 lustreless, 29 shining, 29 splendent, 29 Agate, 11 Almandine, 101 Amethyst, 11 oriental, 85 sapphire, 85 Amorphous stones and their characteristics, 23 Analysis, 5 Aplome, 101 Asters, or asteriated stones, 82, 87-91 Azure-stone, 103 Beryl, 10, 94 colours of, in dichroscope, 34 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 Garnets (A) iron-alumina (called also almandine and precious or oriental garnet), 101 sub-variety, common garnet, 101 (B) lime-iron, 101 sub-variety aplome, 101 melanite, 101 pyreneite, 101 topazolite, 101 (C) lime-chrome, 101, 102 sub-variety uwarowite, 101, 102 (D) lime-alumina, 102 sub-variety cinnamon stone, 102 romanzovite, 102 succinite, 102 (E) magnesia-alumina, 102, 103 sub-variety carbuncle, or anthrax, 102, 103 noble, 103 pyrope, 102 (F) manganese-alumina, 103 sub-variety spessartine, or spessartite, 103 Girdle portion of a stone, 66 Glimmering, in lustre, definition of, 29 Glinting, or glistening in lustre, definition of, 29 Goutte de suif-cut stones, 65 Great Mogul diamond, 64 Green stones, list of, 78 Groups of crystals (see "Crystals") Hardness, physical properties of, 39 table of, 39, 40, 41 Heat indexes, 54 physical properties of, 52 Hollow-cabochon, 65 Hyacinth, ordinary (a form of zircon), 85, 98 oriental, 85 Hyalite (opal), 35 Hydrophane (opal), 35 Imitations and tests of precious stones, 70 Indigo sapphires, 86 Ink sapphires, 85 Iridescence, and cause of, 37, 38 Iron-alumina garnets, 101 Jacinth, oriental, 85 Jarcon, or jargoon, 98 Koh-i-nûr, 64 Lapis-lazuli, 103 Light, physical properties of, 26 Lime-alumina garnets, 102 cinnamon stone, 102 romanzovite, 102 succinite, 102 Lime-chrome garnets, 101, 102 uwarowite, 101, 102 Lime-iron garnets, 101 aplome, 101 pyreneite, 101 topazolite, 101 List of stones according to colour, 75-79 hardness, 39-41 specific gravity, 48-50 Lustre, 26, 28 Lustreless, definition of, 29 Lynx-eye stones, 87 Magnesia-alumina garnets, 102, 103 carbuncle, or anthrax, 102 noble, 103 pyrope, 102 Magnetic and electric influences, 57-61 Malachite, 11 Manganese-alumina garnets, 103 spessartine, or spessartite, 103 Masculine stones, 85 Melanite, 101 Menilite (opal), 36 Metallic-lustre stones, 28, 29 Mohs's table of hardness, 39-41 Noble garnet, 103 or precious opal, 35 Non-diaphanous stones, 28 Odontolite, 106 Olivine corundum (see "Chrysolite"), 85 Opal, 11 varieties of, 35, 36 Opalescence (not to be confused with "Change of Colour" and "Play of Colour," which see; see also "Fire"), 36, 37 Oriental amethyst, 85 cat's eye (see "Cat's eye") emerald, 85 garnet, 101 topaz, 85 Origin of precious stones, 7 Paste, or strass, for imitation stones, composition of, 71 Pavilion portion of cut stones, 66 Pearly-lustre stones, 28, 29 Peridot (see "Noble Chrysolite"), 85 Pink-coloured stones, list of (see also Red), 77 Pinked topaz, 92 Phosphorescence, 26, 30 Physical properties:— A.—Crystalline structure, 13 B.—Cleavage, 19 C.—Light, 26 D.—Colour, 32 E.—Hardness, 39 F.—Specific gravity, 45 G.—Heat, 52 H.—Magnetic and electric influences, 57 Play of colour (not to be confused with "Change of Colour" and "Opalescence," which see; see also "Fire"), 36, 37 Pleochroism, 33 Polarisation, electric, 58, 59 of light, 26, 27 Polariscope, 27, 28 Polishing precious stones, 3, 4 Polymorphism in precious stones, 25 Precious, or noble opal, 35 Pseudomorphism in precious stones, 23, 24 Pyreneite, 101 Pyro-electricity, development and behaviour of, 58-60 Pyrope, 102 Qualities of precious stones, 1, 3 Red and rose-coloured stones, list of (see also Pink), 76, 77 Reflection of light, 26, 28 Refraction of heat, 52-55 light, 26, 27 Reproduction of crystalline form, 20, 21 Resinous lustre stones, 28, 29 Rock-crystal, 11 Romanzovite, 102 Rose-coloured stones (see Red, above), 76, 77 Rose, or rosette-cut stones, 65 Rothschild's testing solution, 73 Ruby, characteristics of, 83 composition of, 10 Sapphire, amethyst, 85 and its varieties, 84, 85 cleared, 86 diamonds, 87 indigo, 86 ink, 85 the blue, composition of, 10, 85 water, 86 Semi-diaphanous stones, 28 Shining, in lustre, definition of, 29 Silica group, composition of the, 11 Silicates, 100 Silky-lustre stones, 28, 29 Single-refraction (see "Refraction") South African diamond (see "Cullinan Diamond") Specific gravity, 45 Splendent, in lustre, definition of, 29 Splitting of the Cullinan diamond, 22 Star-portion of stones, 65 Stars of Africa (see also "Cullinan Diamond"), 22, 64, 68 Starting or splitting of stones on cleavage planes, 23 Step-cut stones, 66 Stones arranged according to colour, 75-79 hardness, 39-41 specific gravity, 48-50 Strass for imitation stones, composition of, 71 Sub-metallic in lustre, definition of, 29 Sub-translucent stones, 28 Sub-transparent stones, 28 Succinite, 102 Synthesis, 5 Systems of crystals (see "Crystals") Table-cut stones, 65 Tallow drops, 65 Teeth of stone, 65 Testing by crystalline structure, 17 hardness, 40, 43 with needles, 41 gems by dichroscope, 33, 34 solution (Rothschild's), 73 Tests of precious stones (general), 70 Topaz, 11, 91 colours of, in dichroscope, 34 oriental, 85 Topazolite, 101 Tourmaline, 96, 97 electric experiments with, 58, 59 Translucent stones, 28 Transmission of heat, 52-56 light, 26 Transparent stones, 28 Trap-cut stones, 66 Tri-morphism in precious stones, 25 Triplets, 72 Turquoise, 104 (bone), 106 composition of the, 11 odontolite, 106 Uwarowite, 101, 102 Violet stones, list of, 78 Vitreous-lustre stones, 28, 29 Water-sapphires, 86 White (paste) stones, 71 stones, list of, 75 Yellow stones, list of, 76 topaz, 92 Zircon, 10, 98 diamonds, 99 Zirconium, 10

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