- Reflection, total, [204]
- Refraction, [4]
- Refraction, double, [8-13]
- Refraction, double, test for, [10], [112]
- Refractometer, [5]
- Rhodolite garnet, [168]
- "Roman" pearls, [279]
- Rose cut stones, [231]
- Rose quartz, [171], [197]
- Rubellite, [93]
- Ruby, [12], [67], [69], [153], [154], [186]
- Ruby, scientific, [99-108]
- Sapphires, [63], [87], [88], [155], [187]
- Sard, [172]
- Sardonyx, [172]
- Scientific stones, [99-108]
- Scientific stones, defects in, [104]
- Scientific stones, tests for, [99-108]
- Siam rubies, [154]
- Silicates, [141]
- "Silk" in rubies, [117]
- Slitting of precious stones, [213]
- South African diamonds, [184]
- Specific gravity, [23-37], [114]
- Sphene, [9], [62], [64]
- Spinels, [71], [90], [123], [140], [158], [188]
- Spodumene, [95], [170], [195]
- Star stones, [44], [46], [157]
- "Step cut" stones, [235]
- Structure of pearls, [258]
- Table, of hardness, [54]
- Table of refraction, [12-13]
- Table of specific gravity, [29]
- Tariff laws, [294-299]
- Test for double refraction, [10]
- Testing hardness, [51-54], [58]
- Testing imitations of pearls, [281]
- Testing unknown gems, [109-118]
- Tiger's-eye, [45], [138], [171]
- Topaz, [67], [73], [91], [124], [145], [159], [189]
- Toughness in stones, [119]
- Tourmaline, [72], [77], [79-81], [96], [146], [167], [194]
- "Triplets," [79], [246]
- Turquoise, [130], [148], [198]
- Unit of weight, [289]
- Wearing qualities of gems, [119]
Diamonds
A Study of the Factors that Govern
their Value