The great tin mine at Viloco (sometimes called Araca) has produced some of the most magnificent Cassiterite specimens extant, and a very small percentage of these pieces are actually associated with tourmaline. This particular specimen consists of several fine, sharp, highly lustrous, brown/black cyclic twinned crystals of Cassiterite measuring up to 2.2 cm across with minor white crystals of Quartz and small acicular greenish-black crystals of Tourmaline. This association is seen in only a handful of Cassiterite specimens from this historic locality. Ex. Brian Kosnar Collection.