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7.—Oblique Cryſtal,
A Cryſtal of 12 Planes, with the Pyramid ſet on obliquely.
b By the Influence of Metals,
8.—Cubic Cryſtal.
Cryſtal ſhaped by Lead.
9.—Pyramidal Cryſtal.
Cryſtal ſhaped by Tin.
10.—Rhomboidal Cryſtal.
Cryſtal ſhaped by Iron.
c Unſhaped.
11.—Pebble Cryſtal.
Cryſtal without Angles in roundiſh Maſſes.
Varieties of Cryſtal.
2. In Colour.
12.—Yellow Cryſtal, called Occidental Topaz.
Cryſtal coloured by Lead.
13.—Blue Cryſtal, called Occidental Sapphire.
14.—Green Cryſtal, called Occidental Emerald.
Cryſtals both coloured by Copper.
Variety of Varieties.
15.—Purple Cryſtal, called Occidental Amethyſt.
3. By Impurities.
16.—Whitiſh Cryſtal.
Cryſtal debaſed by a white Earth.
17.—Brown Cryſtal.
Cryſtal debaſed by a duſky Earth.
And
