This specimen was found about 5-6 months ago (2009), and is one of the more attractive Cassiterite association specimens I've seen. Bolivia has probably produced more tin than any other country in the world. The great tin mines at Viloco (sometimes called Araca) have produced some of the most magnificent Cassiterite specimens extant. This particular specimen is host of several fine, sharp, highly lustrous, black-brown cyclic twinned crystals measuring up to 0.8 cm across which are associated with very attractive Quartz crystals that actually have small Smoky Quartz "phantoms" in the center of the prisms.