POLISHED MUSHROOM JASPER

Mushroom jasper, more accurately known as "Mushroom Rhyolite", is the name for an orbicular rhyolite found in several areas northwest of Phoenix, Arizona. Mushroom rhyolite is a variety of thunderegg: these specimens often include formations of quartz and agate throughout. In some instances, the quartz pocket will contain purple amethyst crystals (quartz var. amethyst). This rhyolite earns its name after the earthy brown to green-colored orbicular formations that in many cases have the appearance of a mushroom cap.