Rhyolite 10mmRhyolite is a felsic mineral (contains a majority of silica) thats made up of tiny crystals within. Some of these are Quartz, Feldspar, Hornblende, and Sanidine. This combination can vary with each piece and alters the color and depth of Rhyolite. This crystal has taken on many names throughout history, but was officially recorded as Rhyolite in 1860 by Ferdinand von Richthofen. If his last name sounds familiar, it's because his nephew was the