Chameleon Diamond with Nickel Absorption Band
Examination of the visible-NIR spectrum revealed a noticeable nickel-related absorption band at 685 nm (figure 2). DiamondView images were taken to prove the stone was not synthetic, as nickel is a common catalyst in HPHT synthetics (figure 3). While nickel has long been known to occur as a trace element in chameleon diamonds (T. Hainschwang et al., “A gemological study of a collection of chameleon diamonds,” Spring 2005 G&G, pp. 20–34), its role in the color-change effect is unknown. Nickel has also been reported as a cause of green coloration in certain diamonds (W. Wang et al., “Natural type Ia diamond with green-yellow color due to Ni-related defects,” Fall 2007 G&G, pp. 240–243), but this may be the first time it has been identified as the major cause of a green component in a chameleon. The rarity of chameleon diamond, combined with the rarity of Ni-related natural green diamonds, makes this a truly unique specimen.
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