Peridot Pyroclastic Bomb Specimens

These are peridot pyroclastic bombs, also called xenolith bombs, with basalt on the exterior and tiny peridot crystals in pockets. We collected these specimens in Peridot Mesa on the San Carlos Apache Reservation in Peridot, Arizona with our friend Stevie Joey. The small holes you see in the basalt were formed when the molten lava flew through the sky in a pyroclastic blast and then cooled abruptly (think the typical very violent volcanic eruption we all studied in elementary school). As that lava went airborne, little pockets of air became trapped in the basalt. Peridot is the gem quality variety of olivine, which only forms in volcanic (igneous) environments. When you see a large peridot crystal, the lava was able to cool very slowly and the crystals have time to grow. When you see small crystals like in these xenolith bombs, the material cooled really quickly which caused these tiny crystals to grow. Peridot is an magnesium iron silicate and iron is actually what gives peridot its d