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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 ") . . 30
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'' . . . . . .83
,. oriental ........ 85
Cinnamon stone . . . . . . . .102
Claims of precious stones ....... 4
Cleavage affecting tests ....... 43
., and " cleavage " as opposed to ' break " . 19. 22
Colour........20, 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—clinorhombie, mouosym-
metric, oblique ... 16. 17
,, (6) Tricliuic—anorthic, asymmetric 16. 17
treatment of . . . . . . .14
Culasse portion of stones ....... 66
