In international coloured gemstone trade, all the asking price and bid price are given according to the total quality grade (1 to 10 ) and carat of coloured gemstones.

国际贸易中有色宝石的报价主要是按其总品质级别和克拉质量给出的。

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"It is a world record for a Golconda diamond and a world record price per carat for a colourless diamond, " Francois Curiel, director of the international jewellery department at Christie's, told reporters.

BBC: 'Perfect' Archduke Joseph diamond sells for $21m