Unusual natural pink diamonds displaying faint yellow color zoning and strong yellow fluorescence are studied in the Carlsbad laboratory.
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At the AGTA and GJX shows, China Stone (Bangkok) marketed a selection of tiny, precisely cut natural gemstones.
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Two small, near-colorless stones reportedly from Myanmar (0.11 and 0.24 ct; figure 1) were recently loaned to GIA for examination for identification.
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The stone owes all of its green color to these shallow radiation stains.
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GIA recently examined a rare orange diamond that demonstrated the complexity of diamond color origin.
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The New York lab encountered another large HPHT-treated diamond that showed stronger pink coloration.
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A combination of trace-element analysis and UV-visible spectroscopy clearly indicated that the yellow color originated from the much more effective chromophore known as “trapped holes,” associated with the trace amount of Mg and Cr in this stone.
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The outstanding feature of this diamond was the extremely strong emission at 578.9 nm, with possible side bands at 586 and 593 nm.
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Recently, an unusual 0.94 ct Fancy yellow-brown emerald cut was submitted to GIA for a synthetic diamond grading report. It contained a cloud of black needle-like inclusions occurring along a plane and showed weak green transmission with fiber-optic illumination.
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