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Ch. 17: The Diamond Market

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152 THE DIAMOND MINES OF SOUTH AFRICA
" Close goods" are pure, well-shaped stones; " spotted stones" are crystals slightly spotted; and " rejection" stones seriously depreciated by spots. Broken stones are grouped under the head of " cleavage." Flat crystals formed by the distortion of octahedra are classed as flats, and flat triangular crystals, which are in reality twin stones, are marked as maacles. " Rubbish " is the refuse, ranking a little better than the lowest grade of all, ordinary "boart" the material used for polishing purposes. Round or shot boart is found in the mines at
Kimberley and is very valuable for use in diamond drills since the Brazilian carbonado has become so scarce. Well-formed shot boart, averaging about the size of peas, sells readily for £6 a carat.
After this separation has been made, the first eight classes are each further subdivided according to their shades of color. The scale is given below in descending order of purity —
Blue White, First Cape, Second Cape, First Bye, Second Bye, Off Color, Light Yellow, Yellow.
Only the first grade, or close goods, are carefully distin­guished by separation of all eight shades. For other classes a
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