40 A Book of Precious Stones
9,
Rubbish; 10, Bort. In the language of the diamond producers " Close
goods" are pure stones of desirable shapes; " Spotted stones " are
crystals slightly spotted; and " Rejection " stones are those seriously
depreciated by spots. " Cleavage" means broken stones. " Flats " are
flat crystals formed by the distortion of octahedral crystallisation;
and flat triangular crystals—twin stones—are " maacles." The refuse is
classed as " rubbish," and common bort or " boart" is polishing
material, while round, or shot, bort, found at Kimberley, is now
valuable for diamond drill points, since Brazilian carbonado has
become scarce.
The
first eight classes are further subdivided according to shades, as:
Blue White, First Cape, Second Cape, First Bye, Second Bye, Off Colour,
Light Yellow and Yellow. Only the " close " or first grade is actually
assorted according to these eight shades; with the other grades the
sorters are less particular. The ten expert sorters, all Europeans, use
no magnifying glasses in their determinations, which are achieved with
marvellous accuracy and rapidity. The assorted diamonds are divided
into little heaps on a long table covered with white paper; the number
of diamonds and their average
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