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Pearls, 11, 161-163.
Pearly lustre, 17.
Pegmatite, 7, 10, 110.
Peridote, 66.
Peridotite, 6, 72, 107, 109, 140.
Phenacite, 158.
Phosphates, 12.
Phosphorescence, 18, 70, 101.
Phrase, 143.
Physical properties, 19-29.
Piezo-electricity, 19, 134, 135.
Pigeon's blood ruby, 103.
Pigott diamond, 98.
Pinacoids, 15.
Pitt or Begent, 74, 96.
Plane of polarization, 141.
Plasma, 143.
Play of colours, 4, 17, 41, 69.
Pleochroism, 38-39, 40, 62, 64.
Polarizing microscope—petrological microscope, 29, 40.
Polishing of gems, 18.
Pre-Cambrian age, 8, 74.
Precious metals for mounting, 65.
Precious stones, 18; qualities of, 2-3.
Prehnite, 158.
Premier Mine, 10, 83, 84.
Price of ruby, 106.
Primary minerals, 6.
Prisms, 15.
Properties of gems, 2-4.
Pushparagam, 128.
Pycnometer, 23-24.
Pyro-electricity, 19, 134.
Pyrope, 130, 131, 132.
Q
Quartz,
4, 7, 10, 14, 19, 22, 57, 58, 108, 128, 135, 140, 141; intro-duction,
140-141; uses, 141; grades, 142-145; industry and marketing, 145-146.
R Radium, 16.
Radium treatment, 56, 58. Raman, Sir C. V., 70.
184
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