San Carlos, Arizona, USA
This is a huge cabinet specimen of peridot. Peridot (olivine) crystallizes early from a cooling magma, and these chunks have been trapped in the resulting porous basalt (is that a contradiction?). Many other minerals can be seen in some of the gas pockets with the aid of a high power loupe. The peridot is the typical green and the larger crystals are transparent. None show any indication of crystal form - I believe that all of the thousands of crystals in the half-dozen pockets of peridot have been damaged. A pocket on top is much darker in color (probably weathered), and the peridot there is is very dark, almost black, and displays an irridescent sheen in purples, greens, and blues. There is a lot of peridot on this specimen.