47 x 25 x 25 mm, fine twin crystals individually to 12 mm. From the collection of Robert Ferguson of Raith (1769-1840). In late 1997, Robert Ferguson's descendants sold the extant portion of the collection to Brian Lloyd (of Gregory, Bottley & Lloyd, London). Some of this material, including this chalcocite, was then resold to Rob Lavinsky (The Arkenstone).

James Sowerby dedicated his Exotic Mineralogy of 1811-1820 ito Ferguson as follows:
"To Robert Ferguson F.R.S., a gentleman known as possessing a Cabinet of rare Foreign Minerals, and who generously volunteered his aid in this undertaking, I do myself the honor to dedicate this Volume. That it may be as equal to his expectations in my part as the subjects are important, is the great desire of his humble servant, James Sowerby."