Cassiterite variety Needle Tin
Minera Monserrat, Challapampa, Poopo Province
5.6 x 5.5 x 3.4 CM (cabinet)
A very unusual specimen from Boliva that looks like an old Cornish "needle tin". A three dimensional matrix densely covered with delicate accicular crystals of brown Cassiterite. In fine condition as seen, ex. Hitchings collection. Especially impressive under magnification, this is an uncommon habit and a well crystallized example.
A fine and attractive example of this rare Lead, Silver, Antimony "black ugly" mineral! Until the 2004 find, Andorites were one of the rarer Sulfosalts and crystals were always quite tiny. This piece is from that discovery and a very good value for the size, condition and form. The metallic luster and steel to brassy hues are as good as these ever get. Ex Kosnar, there are now very few of this caliber to be found, lesser pieces are typically far more expensive!
Franckeite (var Potosiite)
San Jose Mine, Oruro
7.5x4.6 CM (small cabinet/ large miniature)
Potosiite is the rare Tin poor variety of the rare mineral Franckeite, and was a separate species until it was discredited in 1997. It is still a very rare Sulfide with crystals larger than micros considered huge. From a small find of the worlds largest and best crystals at the San Jose mine, this is a top example with individual crystals to 1.3 cm. For this rare and ugly mineral this is a true killer and even esthetic! This was rated as one of the best 7 pieces found.