Double refraction, 37-38, 69.
Dodecahedron, 13, 15, 67, 68, 86.
Domes, 15. '
Dop, 51, 53-54.
Double refraction, 37-38.
Doublet, 64, 65.
Durability, 4.
E
Electricity, factional, 19; piezo-, 19; pyro-, 19.
Electrical properties, 19.
Elements, 11.
Emerald, 1, 3, 4, 6, 8, 12, 14, 19, 45, 58, 122, 123, 124, 125, 126. „ mines of Egyptian Red Sea coast, 2.
Emery, 101, 103, 104.
Engraving, 55.
Enstatite, 156.
Etched figures, 68.
i
Euclase, 156-157.
Excelsior diamond, 99.
Extraordinary rays, 37, 40.
F
Facetted cutting, 42.
Felspar, 157.
„ crystals, 7.
Fire, 2, 4, 17, 31, 33, 42, 45, 69, 103. » „ opal, 146.
Flint, paste or strass, 19, 64, 140, 143.
Flint glass, 64.
Florentine brilliant, 97-98.
Fluorescence and phosphorescence, 18.
Fluorescence in diamond, 18, 70-72; in corundum, 18, 103.
Fluorite, 11, 17, 128, 136, 157-158.
Forms of crystals, 12-16.
Fossil wood, 141.
Fox, Sir C. 8., 75. ,
Fracture—conchoidal, splintery, 22.
Frictional electricity, 19.
G
Gaudin, 60.
Garnet,
8, 11, 42, 107, 108, 131; introduction, 129; physical properties and
composition, 129-131; grades 131-132; occurrence, etc., 132-133.
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