Monday, May 19, 2008
As Ron, MJC and Silver Fox have guessed correctly the sample from this weekend's weekend fun is largly Sphalerite. Ron restrained himself to naming the Quartz glomerocrysts that can also be found intergrown with milky Quartz and sulfides on the backside of the sample (but very tiny). All the big cubic crystals are tetrahedral (few truely idiomorph) Sphalerite. Considering the dark color these Sphalerites likely have a high iron content. I don't know how high and if it would be enough to consider these Marmatite. On a few spots the Sphalerite is actually almost transparent and has an orange to reddish color. Furthermore we have massive Galenite, Pyrite (but no large crystals Silver Fox) and Chalkopyrite on the outer edges of the sample. The sample is a gift from Peru. I assume it comes from a vein type deposite somewhere in the Andes of Peru or Bolivia.