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Oriental amethyst ........ 85
cat's eye (see " Cat's eye ")
„ emerald ........ 85
,. garnet ........ 101
., topaz......... 85
Origin of precious stones ....... 7
Paste, or stress, for imitation stones, composition of . .71 Pavilion portion of cut stones ...... 66
Pearly-lustre stones ....... 28, 29
Peridot (see" Xoble Chrysolite") • • • • .85
Pink-coloured stones, list of (sue also Red) .... 77
Pinked topaz ......... 92
Phosphorescence ....... 20. 30
Physical properties:—
A.—Crystalline structure ..... 13
B.—Cleavage ....... 19
C— Light........26
D.—Colour ....... 32
E.—Hardness ....... 39
F.—Specific gravity ...... 45
G.—Heat........52
H.—Magnetic and electric influences . . . 57 Play of colour (not to be confused with " Change of Colour "
and " Opalescence," which see; see also " Fire ") . 36, 37
Pleochroism ......... 33
Polarisation, electric ...... 58. 59
of light......26, 27
Polariscope........27, 28
Polishing precious stones . . . . . . . 3, 4
Polymorphism in precious stones ..... 25
Precious, or noble opal ....... 35
Pseudomorphism in precious stones . . . . 23, 24
Pyreneite ......... l01
Pvro-electricity, development and behaviour of . . 58-60
Pyrope..........102
Qualities of precious stones . . . . . .1,3
Red and rose-coloured stones, list of (see also Pink) . 76, 77
Reflection of light....... 26,28
Refraction of heat ....... 52-55
light....... 26, 27
Reproduction of crystalline form .... 20. 21
Resinous lustre stones ...... 28, 29
