Ottensite on antimonite – Qinglong Mine, Dachang, Guizhou, China
Ex Berthold Ottens collection
 
Only rarely do you have the opportunity to get hold of a mineral from the collection of its namesake. 
This beautiful collection piece of the extremely rare antimony oxide Ottensite on antimonite comes from the collection of Berthold Ottens, after whom this mineral was named.
Ottensite is a supergene product of the weathering of stibnite (antimonite). It forms crust-shaped aggregates up to 1 mm thick on stibnite crystals. Ottensit consists of spherical aggregates with a diameter of up to 0.3 mm.