Helvine

Helvine, or Helvite, a mineral which forms lustrous regular crystals of a yellow or green colour, specific gravity 3-8, hardness 6. It consists of the silicates of iron, manganese, and beryllium with a sulphide of manganese, and is interesting both as a compound of the rare element beryllium, and as the only known natural compound of a silicate and a sulphide.