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

LONDON: PRINTED BY WILLIAM CLOWES AND SONS, LIMITED,
GREAT WINDMILL STREET, W., AND DUKE STREET, STAMFORD STREET, S. E.