- Cobaltite on Skutterudite
- Schneeberg, Saxony, Germany
- Thumbnail, 2.7 x 1.9 x 1.2 cm
- Ex. Sir Robert Ferguson
This old-time specimen of cobaltite, a sulfide composed of cobalt, arsenic, and sulfur, was once part of the late 18th Century collection of Robert Ferguson. It features an equant, splendent, silvery cobaltite crystal 6 mm across perched on matrix of skutterudite and minor erythrite. The specimen is accompanied by a very old label on parchment. This superb competition-level thumbnail specimen dates to the collection of Sir Robert Ferguson (1769-1840). He was a member of Parliament and the nobility from Kirkaldy, Scotland (he had stopped collecting by 1810, it is thought). I purchased it in London when his collection was dispersed in 1998 and sold it to a collector at that time.