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346 Glossary
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Cleaving. Splitting a crystal in a direction in which it may most easily be done—along the grain.
Close Goods. Pure stones, of desirable shapes; highest class of South African diamonds, as assorted at Kimberley.
Clouds. Muddy
or cloudy patches of any colour in a stone which, when brought to the
surface by cutting, are ineradicable. " Flat, subtransparent blotches
along the grain of a stone."—Cattelle.
Colour-Play. (Play of Colours.) Prismatic colours produced by dispersion of light.
Colour Range. A statement of the various colours exhibited by different specimens of a mineral.
Combustibility. A quality possessed by the diamond only, among gems.
Concentrates. Gem or mineral ore or ground reduced by mechanical or chemical processes to its minimum in bulk or weight.
Conchoidal. Shell-like fracture of any mineral.
Concretions. Mechanical
aggregation, or chemical union of particles of mineral forming balls or
irregularly shaped nodules in strata of different material.
Conglomerate. Pebbles or gravel bound together naturally by a silicious, calcareous, or argillaceous cement.
Corundum. Crystallised alumina—rubies, sapphire, etc.
Cradle. Trough in which, by a rocking motion, placer miners wash auriferous or gem gravels.
Crystallography. The science which describes or delineates the form of crystals.
Crystals. Trade term for fourth grade cut diamonds; colourless diamonds.
CULASSE. Portion of brilliant-cut diamond below the girdle.
Culet. (Or Collet). Bottom facet of brilliant parallel to the girdle.
Curator. One to whose official care is entrusted a department—as of mineralogy—in a museum.
Diamond. The
mineral gem alone composed of pure carbon; crystallises in the
isometric, or cubic, system; combustible, it can be totally consumed,
disappearing
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