We all have them, but in the mineral world the continual exchange of specimens between collections, dealers and other collectors means that provenance and history can play an important part in the interest in a particular specimen.
When we were recently reviewing Peter Uerpmann's collection one piece of particular interest to Peter was "an unnamed molybdenum and antimony mineral" that Georg Gebhard have given him.
The mineral was featured in the Gebhard book Tsumeb II and there it was in the collection. Of course some time has passed since the book was written and the unnamed mineral has now been described as biehlite.
As someone who handles quite a few minerals it is quite fun spotting an old TVM label at a show, or even seeing a specimen elsewhere in another display.
This much prized ex Warren Taylor (ex TVM) South African rhodochrosite has recently put in another appearance in the displays at the Denver Show.
Glad to see it is keeping well!