These specimens came out about two years 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 who are familiar with 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 sharp, twinned crystals of Stannite sitting atop and mixed with a matrix of acicular Jamesonite crystals and are associated with minor gemmy brown Cassiterite crystals. Stannite is copper iron tin sulfide and some of the best pieces of this material come from this mine. This is a very choice specimen of a hard to find association from Bolivia. A very unique specimen for these rare minerals.