Mineral Species: Tephroite

Chemical Formula: Mn2SiO4

Chemical Name:  Manganese Silicate

Mineral Class: Nesosilicate

Mineral Notes: Tephroite is a rare silicate named for the typical colour which is ash gray ("tephros"  Greek for ash). It belongs to the Olivine group and forms a series with Fayalite. Tephroite is the manganese rich member of the series and Fayalite is the iron rich member with a formula of Fe2SiO4. Unlike Fayalite which is more commonly found in volcanic rocks, Tephroite occurs in contact metamorphic zones and is often a hydrothermal replacement mineral. It also forms a series with Forsterite.

Description: A brown-grey matrix of Tephroite. Within the body of the specimen individual crystal faces are easily seen and present as lustrous dipyramidal outlines. The specimen also probably contains Ericssonite and Rhodonite, but these are unconfirmed.

Location: Langban, Varmland, Sweden.