These specimens came out about a year ago, and until recently, their identity wasn't known for sure. From the beginning they were speculated as being Stannite with Jamesonite, and that's what they turned out to be. Most people interested in Bolivian minerals are probably familiar with the classic Stannite and Zinkenite association specimens from San Jose that were found circa WWII, but these new specimens are much rarer and are the only association of Stannite with Jamesonite that I have seen from any locality. The specimen features several small, sharp, lustrous, metallic, "brass" colored crystals of Stannite sitting atop and mixed with a matrix of bright, metallic, needle-like Jamesonite crystals. Stannite is copper iron tin sulfide and some of the best pieces of this material come from this mine.