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  • Enlargement showing crowningshieldite
  • Crowningshieldite (circled)

Crowningshieldite, new mineral unveiled

The Gemological Institute of America (GIA) announced the discovery of crowningshieldite, a new mineral discovered from the Letseng mine in Lesotho in southern Africa, in October 2018 after being accepted as a mineral by the International Mineralogical Association in September.


Named in honour of GIA’s veteran researcher G Robert Growningshield, the mineral was found by a group of researchers from GIA and the University of Padova as an altered inclusion in two diamonds from the mine.


GIA research scientist Evan M Smith told Hong Kong Jewellery more about the new discovery at a recent interview.


What are the gemmological specifications of crowningshieldite?

Crowningshieldite is a nickel sulfide, and is essentially a high temperature polymorph (having the same composition but different crystal structure) of millerite. In general, it should be expected to have properties similar to millerite. The detailed properties of the new mineral crowningshieldite will be described in a future, peer-reviewed scientific publication.


Is it a gem-quality mineral?

Crowningshieldite itself is unlikely to be suitable as a gem mineral. However, it is closely

associated with a gem material, diamond. Crowningshieldite was discovered in a gem-quality diamond, inside an inclusion. Diamonds can contain a wide variety of different minerals as inclusions.


Is the availability of the mineral sporadic in diamond mines?

The new mineral crowningshieldite has only just been discovered. It occurs as very small

grains in a special kind of inclusion. It may be present in other diamonds, from other mines, but it requires very detailed examination in a laboratory in order to identify it. This is a very rare and fine-grained mineral, and it is unlikely that we will find large pieces of it that could be recognised easily.


What is the significance of the new discovery for GIA and the gemstone industry?

This discovery highlights the strength of GIA’s ongoing research program. Naming the

mineral after G Robert Crowningshield, a pioneering figure in GIA, is an important gesture in recognising the immeasurable contributions he made, both in developing the scientific rigor of GIA research and in advancing the field of gemmology. This new mineral, which has been found in diamond, serves to draw attention to the complexity and allure of natural diamonds, and especially in this case, to CLIPPIR diamonds. There is so much that scientists are learning about the earth by studying diamonds. (Photo courtesy: GIA)


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