Ferrous orthosilicate, Fe₂SiO₄

Ferrous orthosilicate, iron olivine or Fayalite, Fe₂SiO₄, occurs as tabular rhombs in iron slags, of which it is one of the commonest constituents. Its name is derived from Fayal Island (Azores), where it was first found, although probably even that specimen was originally a lump of slag from a ship's ballast. Its crystal elements are: -

a: b: c = 0.4632: 1: 0.5835.

It is the most fusible silicate present in slag, and melts at about 1260° C. When heated in hydrogen, reduction begins at 225° C.