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GIA scientists uncover new mineral

11 October 2018

Diamond sample that contains the newly recognised mineral crowningshieldite


The Gemological Institute of America (GIA), in collaboration with researchers at the University of Padova, recently discovered crowningshieldite, a new mineral named in honour of gemmological maven G. Robert Crowningshield.

According to GIA, G. Robert Crowningshield was a pioneering figure in gemmological research for more than 50 years at GIA.

The mineral crowningshieldite was discovered as an altered inclusion in two diamonds from the Letseng mine in Lesotho. GIA Research Scientist Dr. Evan M. Smith and his team of researchers unearthed crowningshieldite while examining inclusions in CLIPPIR diamonds – a variety of Type IIA diamond that forms at significantly greater depths than most diamonds. Crowningshieldite is a nickel sulfide mineral with a hexagonal crystal structure and can be regarded as the high-temperature polymorph of the mineral millerite. It is also the naturally occurring analogue to the synthetic compound known as α-NiS. The mineral is proposed to have formed by alteration or chemical modification of originally metallic, polyphasic inclusions. These iron and nickel-rich metallic inclusions are the most prevalent type of inclusion found in CLIPPIR diamonds.

“Discoveries such as this propel our understanding of diamonds and the earth forward; this is why research is the cornerstone of GIA’s mission,” said Tom Moses, GIA executive vice president and chief laboratory and research officer.  “I can think of no better way to honour Mr. Crowningshield’s legacy.”

G. Robert Crowningshield took GIA and the young science of gemmology to new scientific heights. His first breakthrough came in 1956, when he discovered and documented the spectroscopic feature characterising yellow irradiated diamonds. In 1971, he wrote the first report on gem-quality laboratory-grown diamonds. His observations about the identification criteria for laboratory-grown diamonds discussed in that article, such as colour zoning, metallic inclusions and uneven patterns of UV fluorescence, are still used today for diamond identification. Crowningshield is also recognised for reporting on many discoveries about pearls and coloured stones. His 1983 landmark article described a naming convention for orange-pink “padparadscha” sapphires and he published more than a thousand brief observations in the regular Lab Notes column – that he originated in 1957 – of Gems & Gemology, GIA’s quarterly professional journal.