7.35" Green Jasper Replaced Petrified Wood Bookends - Oregon

Jasper is a term that can be applied to an opaque variety of chalcedony. The opaqueness is due to a higher concentration of impurities mixed with silica/quartz compared to other varieties of silica, such as quartz or agates. Like agate it may form in a wide variety of colors, and is often multi-colored. In most cases, jasper forms when silica-rich fluids permeate throughout a soft sediment or volcanic debris deposit. The fluids then crystallize around the particles/impurities, resulting in a cementation process. Most often, the impurities present determine the coloration of the deposit following solidification, but other factors can play a role in the color of what is now considered a jasper.