Olivine and Staurolite

Staurolite, a dark coloured mineral that is a silicate of aluminium and iron, has some free silica content but much less than silica sand. It is marketed in the USA, where it naturally occurs, as an alternative to silica sand, in Europe, olivine, which is quarried in Norway, is marketed as silica free sand. It is a silicate if iron and magnesium. Olivine, which is pale green, is often used to clean buildings. It is also sometimes specified for non-ferrous substrates instead of synthetic abrasive. Olivine is very hard but tends to fracture on impact, creating lots of light coloured dust.

Both Staurolite and Olivine are relatively high-priced abrasives in most markets due to their limited geographic availability.

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