Unusual, lithium-bearing pyroxene, LiAlSi2O6; sp. gr. 3.0–3.2; hardness 6.5–7.0; monoclinic; usually greyish-white, often with a greenish or yellowish-green tinge, occasionally violet, transparent to translucent; vitreous lustre; crystals prismatic, often striated, etched, and corroded, also occurs massive and columnar; cleavage perfect prismatic {110}, parting {100}; typically occurs in lithium-rich granites and pegmatites, associated with lepidolite, tourmaline, and beryl. The green variety (hiddenite) and the lilac variety (kunzite) are used as gemstones, otherwise it is an ore mineral of lithium.