Aerinite (Ca)10Si ) is a bluish-purple inosilicate mineral. It crystallizes in the monoclinic system and occurs as fibrous masses and coatings. It has a dark, vitreous luster, a specific gravity of 2.48 and a Mohs hardness of 3.
It is a low-temperature hydrothermal phase occurring in zeolite facies alteration of mafic rocks. Associated minerals include prehnite
Its name comes from a Greek "aerinos," meaning "atmosphere" or "sky".