METHOD OF DYEING SUBQUALITY DIAMONDS TO GIVE THEM BLACK COLOR Russian patent published in 2002 - IPC

FIELD: diamond processing. SUBSTANCE: diamonds are heated in vacuum being simultaneously exposed to polychromatic light emission and magnetic field. Heating temperature is chosen in dependence on density of micro- and macrodefects of diamonds within a range of 1200 to 1400 C. Under such conditions, valence-unsaturated nitrogen impurities, plastic deformations, and other imperfections are graphitized in the form of small powder-like carbon particles or form intermediate graphite-like complexes, which impart black color to diamonds. EFFECT: improved appearance of diamonds and improved environmental condition. 2 cl