Chalcedony, 141, 142, 143.
Chiastolite, 155.
Chlorastrolite, 156.
Chlorospinel, 117, 118.
Chrysoberyl,
11, 63, 108; introduction and physical properties, 119; grades, 120;
mode of cutting, 120; occurrence, 121; celebrated Cat's eyes, 121.
Chrysolite, 120, 121, 139.
Chrysophrase, 141, 142.
Cinnamon-stone, 131.
Citrine, 55, 141, 142.
Cleavage, 21; octahedral, 50; dodecahedral, 68. „ perfect, imperfect, distinct, indistinct, 21.
Colombia, emerald mines of, 10.
"
Colour, lustre, beauty, etc., of gem-stones, 4, 16-19.
Coloured diamonds, 100-101.
Colouring matter, 16.
Compound crystals, 16.
Composition of gem minerals, 11, 12.
Corals, 11, 163-164.
Corundum, 3, 6, 7, 8, 11, 37, 60, 61, 63, 101, 106, 107, 110, 118.
„ Family (ruby and sapphire)—introduction, 101; physical
characters,
101-103; uses, 103-104; grades, 104-105; ruby cutting, 105; price of
ruby, 106; medicinal powers attributed to ruby, 106; occurrence,
106-108; gem mining, 108-113; mar.
. keting, 113-115; celebrated rubies, 115-116.
Cracks, internal, 62.
Cretaceous, 6.
Critical angle of total reflection, 31, 32, 33.
Crookes, Sir William, 59.
Crookshank, H., 125.
Cryptocrystalline, 19.
Crystalline aggregates, 19.
Crystal angles, constancy of, 13. Crystal form, 14; system, 13-14. Crystalline
structure, 12. Crystals, forms of, 12; size of, 13. Cube, 13, 14. Cubic
system, 13,14. Cullinan diamond, 99. Cut stones, forms of, 42-45.
Cutting of gems, 12, 18, 41, 45-46; other gems, 54-55. Cyanite, 156.
