weight for precious stones. Karat is used to indicate degrees of quality in gold.
Carbon. A
tetrad (having four sides), non-metallic mineral element occurring in
two crystalline forms, diamond and graphite, and one amorphous form,
coal.
Carbon Dioxide. Carbonic acid gas; a colourless gas 1524 times as heavy as air and twenty-two times as heavy as hydrogen.
Carbon Spots. Opaque black spots in the body of a diamond.
Carbonado. Brownish,
black variety of diamond; large pebbles or masses of diamonds, nearly
pure carbon. Carbonado was formerly chiefly found in great quantity—now
decreasing—in Bahia diamond district, Brazil; used to point rock drills
and, reduced to powder, for polishing diamonds.
Carbuncle. Garnet—sometimes, ruby, spinel, or other red gem—cut convex or en cabochon: there is no such specific mineral.
Cat's-Eye. A term applied to gem minerals which, when cut convex (en cabochon), display
a band of light, usually across inclusions of parallel fibres of
asbestos; name derived from resemblance to the eye of a cat.
Ceylon Ruby. A ruby having a pink tint.
Chalcedony Patches. Milk - like semi - transparent patches which sometimes occur as faults in rubies.
Change op Colours. Manifested in minerals like Labrado-rite, where the colours change as the stone is turned.
Chatoyancy. Changeable or undulating lustre or colour, as displayed by a cat's-eye.
Chips. Cleavage of diamonds of smallest fractions of a carat in use.
Clatersal. Diamond splints, which are converted into diamond powder by crushing.
Clean. Free from interior flaws.
Cleavage. Direction
within a crystal along which there is minimum cohesion; diamond
crystals which require cleaving; pieces cleaved from the crystal.
