Experimental results of the atmospheric-pressure high-temperature treatment of dark brown type Ia natural diamonds were considered. The atmospheric-pressure high-temperature treatment was carried out under the atmospheric pressure using an experimental homemade system. The samples were placed in the inert gas current and subjected to 5 or 6 repeated thermal shocks, i.e. the diamonds were sharply heated to 1300–2100C. As a result, the original brown colour of the samples was considerably reduced. The IR absorption intensity of the main A and B nitrogen centers was not observed to change. However, photoluminescence due to N3 and H3 centers was observed in the treated samples.

APHT Treatment of Brown Type Ia Natural Diamonds: Dislocation Movement Or Vacancy Cluster Destruction? V.G.Vins, A.P.Yelisseyev, S.S.Lobanov, D.V.Afonin, A.Y.Maksimov, A.Y.Blinkov: Diamond and Related Materials, 2010, 19[7-9], 829-32