My Fascination with Rocks...
Aphanitic Volcanic Bomb. A volcanic bomb found in the Mojave Desert National Preserve. The smooth texture of this basaltic volcanic bomb is aphanitic. A volcanic bomb is a mass of molten rock (tephra) larger than 64 mm (2.5 inches) in diameter, formed when a volcano ejects viscous fragments of lava during an eruption. They cool into solid fragments before they reach the ground. Because volcanic bombs cool after they leave the volcano, they do not have grains making them extrusive igneous rocks.
Mexican Fire Agate a variety of chalcedony (SiO2), is a semi-precious natural gemstone found only in certain areas of northern Mexico and the southwestern United States.There is no actual object inside the stone, this special effect arises from light interference within the microstructure layering of the gem. Captain Tenneal's photostream. Shaped and polished piece.
Rainbow Calsilica is a microcrystalline calcite bonded with the amorphous clay mineral allophane. Silica is also present. It has been described as vein matter or fracture fill formed when a copper push cut into volcanic rhyolite host rock. A stabilization process similar to that used with turquoise has been applied to it.
Hemimorphite on Apatite pseudo