Gedrite is an amphibole with the mineral formula of (Mg,Fe)5Al2(Si6Al2)O22(OH)2. It occurs in metamorphic rock and is a variable of anthophyllite. This sample i — Photo: Shannon Heinle · CC0
Gedrite
An orthorhombic magnesium-iron amphibole — a double-chain inosilicate of metamorphic rocks.
Intro adapted from Wikipedia (CC BY-SA).
Gedrite is an IMA-recognized mineral species in the silicate class, with the chemical formula Mg₂(Mg₃Al₂)(Si₆Al₂)O₂₂(OH)₂.
It crystallizes in the orthorhombic crystal system (space group Pnma). It is a member of the Amphibole structural group.
Key properties: Mohs hardness 5.5–6; specific gravity 3.15–3.26; typically brown or green or gray; white streak; Vitreous luster; refractive index 1.681; optically biaxial.
IMA symbol Ged, IMA status: approved, named in 1836.
Widespread in medium- to high-grade metamorphic rocks; in metasomatized contact metamorphic rocks.
It is found associated with Garnet, cordierite, \hornblende, " anthophyllite, cummingtonite, sapphirine, sillimanite, kyanite, quartz, staurolite, biotite.
The name refers to the occurrence near Gµedre, France.
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