Rhyolite cabochon in a puffy, pear-shape that measures 1.16 inches by .074 inch.
Rhyolite is an igneous rock. Igneous comes from the word ignis, which means fire in Latin. Think ignite. It has the properties of the fire signs in astrology.
Rhyolite has the same composition as granite, but it is extrusive, meaning it is volcanically-formed as opposed to granite, which is intrusive, meaning it forms below the earth's surface. As Rhyolite cools, it forms a bunch of tiny, even microscopic in size, crystals. If it didn't form any crystals, it would actually be obsidian instead of rhyolite. Granite, which forms inside the magma, cools much more slowly, and tends to produce larger crystals.
If Rhyolite has a lot of holes (vesicules) in it, it is pumice. The Greek word rhyx translates as stream of lava.
July birthday stone.