jasper

An opaque, fine-grained variety of silica — a form of chalcedony colored by mineral impurities into reds, yellows, browns, greens, and grays, often banded or spotted. Jasper is one of the most abundant and varied of the semi-precious stones, found in riverbeds, desert pavements, and volcanic terrain worldwide. It was among the first stones shaped into tools and ornaments. Every color in jasper is the signature of a different iron compound, a different oxidation state, a different chapter of the rock's history.