Gem News International Gems & Gemology, Winter 2018, Vol. 54, No. 4

Crowningshieldite: A New Mineral

Newly recognized mineral crowningshieldite in a diamond sample
 
 
Figure 1. Left: A diamond sample from the Letšeng mine in Lesotho that contains the newly recognized mineral crowningshieldite, in the area circled in red. Right: Electron microscopy reveals individual grains of crowningshieldite in a fine-grained mixture with other minerals. Photos by Evan M. Smith (left) and Fabrizio Nestola (right).

GIA, in collaboration with researchers at the University of Padova, recently discovered crowningshieldite (figure 1), a new mineral named in honor of G. Robert Crowningshield (1919–2006), a pioneering researcher at GIA for more than 50 years. His many landmark contributions included the detection of irradiated diamonds, the initial report on General Electric’s facet-quality synthetic diamonds, and the description of “padparadscha” sapphire’s orangy pink to pinkish orange color. Crowningshieldite is a nickel sulfide mineral with a hexagonal crystal structure and can be regarded as the high-temperature polymorph of the mineral millerite. Discovered as an altered inclusion in two diamonds from the Letšeng mine in Lesotho, it was accepted as a mineral on September 18, 2018, by the International Mineralogical Association.