Minerals identify

Know how to recognize them

Gedrite

Inosilicate, ferromagnesian amphibole group

Gedrite is a crystal belonging to the orthorhombic supergroup of the double chain inosilicate minerals with the ideal chemical formula Mg 2(Mg 3Al 2)(Si 6Al 2)O 22(OH) 2.

Gedrite is the magnesium of a solid solution magnesium cations (Fe), leading to the iron rich endmember 'ferrogedrite', with the formula: Fe2+ 2(Fe2+ 3Al 2)(Si 6Al 2)O 22(OH) 2. However, pure endmembers are very rare, with often either one of the mentioned cations dominating the composition. Thus, the formula can be written in such a way to express common intermediary gedrite samples: (Mg,Fe)2+ 2(Mg,Fe)2+ 3Al 2(Al 2Si 6O 22)(OH) 2.

Divalent manganese (Mn) may substitute for some of the magnesium. Trivalent or ferric 4+ may replace some of the aluminum and chlorine (OH) in amphoboles. Other chemical impurities may include calcium , sodium.

Gedrite also forms a series with another ferromagnesian amphibole, anthophyllite.

Gedrite occurs in contact and medium to high grade metamorphic rocks , cordierite , cummingtonite, kyanite and biotite

Gedrite was first described for an occurrence in Gedres, France in 1836.

Identification

Color of mineral

White
Grey
Brown
Green
Black

Mohs scale ( mineral hardness )

5.5

Density ( specific gravity )

1.671
1.681
1.69

Luster ( interacts light )

Silky
Vitreous

Crystal ( diaphaneity )

Orthorhombic