De Beers Consolidated Mines, 7, 33 -- -- floors at Kenilworth, 47 -- -- Mine, 14, 24, 34 -- -- -- characteristics of diamonds from, 64 -- -- strong-room, 74 Delhi diamond, 107 Density of diamond, 57, 93 -- of graphite, 83, 93 -- of stones accompanying diamond, 70, 71, 93, 95 Depositing floors, 46 Dewar, Sir J., conversion of diamond into graphite, 123 Diabase, olivine, 16 Diallage, 20 Diamond, absorption spectrum of, 101 -- and polarised light, 104 -- a new formation of, 122 -- ash of, 82, 89 -- collector, automatic, 56 -- combustion of, 89 -- -- temperature of, 90 -- converted into graphite, 100 -- density of, 57, 93 -- etched by burning, 88 -- explosion of, 120 -- genesis of the, 115 -- in meteors, 134 -- in Röntgen rays, 107 -- matrix of, 67 -- natural formation of, 127 -- Office at Kimberley, 73 -- physical and chemical properties of, 89 -- pipes or craters, 18 -- radio-activity of, 109 -- refractive index of, 103 -- Trade Act, 36 -- triangular markings on, 87 -- tribo-luminescence of, 100 Diamonds, coloured or fancy, 62, 82 -- Maskelyne on, 1 -- noteworthy, 76 -- phosphorescence of, 96 -- produced, weight, value of, 35 -- yield of, from De Beers, 60 Drift, diamonds from the, 12 Duke of Tuscany diamond, 80 Dutch boart, or zircon, 59 Dutoitspan Mine, 14, 23 -- -- characteristics of diamonds from, 64 Eclogite, 20 -- containing diamonds, 67 Electrons, bombardment by, 98 Emerald, refractive index of, 103 Empress Eugenie diamond, 80 Enstatite, 20 Explosion of diamonds, 120 Excelsior diamond, 80 Fancy stones, 62 Fingoes, 39 Flint glass, refractive index of, 103 “Floating Reef,” 21 Floors, depositing, 46 Fluor-spar, refractive index of, 103 Formation, new, of diamond, 122 Fort Beaufort, 6 Franklinite, 97 Frank Smith Mine, 15 -- -- -- characteristics of diamonds from, 66 Fraserburg, 6 Garnet, 20, 70 -- density of, 93 Genesis of the diamond, 115 “Golden fancies,” 65 Granite, 18 -- density of, 93 Graphite, 81, 83 -- combustion temperature of, 90 -- conversion of diamond into, 100 -- density of, 93 -- diamonds coated with, 99 Graphitic oxide, 83, 93 Grease, collecting diamonds by aid of, 57 Hard blue ground, 47 Hardness of diamond, 90 Haulage system, 46 Hexakis-octahedron crystal, 86 Hope blue diamond, the, 80 Hornblende, 71 -- density of, 93 Iceland spar, refractive index of, 103 Ice, refractive index of, 103 I.D.B. laws (Illicit Diamond Buying), 36 Ilmenite, 20 India, diamonds in, 4 Inverel diamonds, 91 Internal strain in diamonds, 104 Iron a solvent for carbon, 116 -- ore, density of, 93 -- pyrites, 20 Jagersfontein diamond, 79 -- Mine, 14 -- -- characteristics of diamonds from, 68 Jeffreysite, 20 Kafirs, 42 Kamfersdam Mine, 15 -- -- characteristics of diamonds from, 66