Similar to olivine, pyroxene does not refer to a single mineral, but rather to a diverse group of silicate minerals. Members of this group exhibit variable composition and color, appearing in hues of white, yellow, green, brown, and black. Found in almost all volcanic rocks, as well as many metamorphic ones, René-Just Haüy coined the collective name of these minerals from the Greek words for “fire” and “stranger,” which is indicative of his assumption that these crystals were somehow accidentally introduced into the lava samples he was studying. Extremely widespread, pyroxenes also occur in many samples of lunar rocks.