An isometric mineral, 2(Mn₄Be₃(SiO₄)₃S) ; manganese may be replaced by iron toward danalite, or by Zn toward genthelvite; forms tetrahedra; Mohs hardness, 6 to 6- 1/2; in veins with quartz, hornblende, and iron oxide; in pegmatites, and some alkaline igneous rocks.