The monoclinic sodium aluminum pyroxene, NaAlSi₂O₆. Free crystals are rare. Jadeite usually occurs as dense, felted masses of elongated blades or as fine-grained granular aggregates. It has a Mohs hardness of 6.5 and a density of 3.25–3.35. It has a vitreous or waxy luster, and is commonly green but may also be white, violet, or brown. Jadeite exhibits the 93° and 87° pyroxene cleavages and a splintery fracture. It is extremely tough.