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Cabochon
polished gemstone with an oval shape
Cachalong
old term used to describe a porous opal
which becomes translucent on immersion in
water
Carnelian
sometimes spelt cornelian.A reddish to orange
coloured form of chalcedony
Chalcedony
form of quartz composed of minute crystallites
Chalk
(geological); massive, white, fine-grained
form of calcite
Chert
greyish chalcedony, commonly occurring as
bands in limestone.
Chrysoprase
green, gemstone form of chalcedony
Cinnabar
natural form of mercury sulphide, red in
colour
Citrine
gemstone, yellow variety of quartz
Coesite
a type of silica formed at high pressures
Colloid
an ultra-fine suspension of solid in liquid
Copi
a term used in the opal fields for a white
clay; also used to denote a powdery gypsum
Cristobalite
a type of silica formed at high temperatures |
