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 hosts fine, sharp, highly lustrous, black, cyclic-twinned crystals of Cassiterite associated with very gemmy prismatic colorless Quartz crystals on matrix. Some of the Quartz crystals have tiny Smoky Quartz "phantoms" in the center of the prisms.