Gedrite

{{Infobox mineral | name = Gedrite | category = Inosilicate | boxwidth = | boxbgcolor = | image = | caption = | formula = (Mg;Fe²⁺)₂[(Mg;Fe²⁺)₃Al₂](Si₆Al₂)O₂₂(OH)₂ | molweight = | color = White, gray, brown, green | habit = bladed and prismatic crystals; fibrous and sheath like aggregates. | system = Orthorhombic; 2/m 2/m 2/m | twinning = | cleavage = 56 and 126° - good; {210} perfect | fracture = Splintery | mohs = 5.5 - 6 | luster = Vitreous to silky | refractive = nα = 1.671 nβ = 1.681 nγ = 1.690 | opticalprop = Biaxial (+) | birefringence = δ = 0.019 | pleochroism = Weak to moderate | streak = | gravity = 3.18 - 3.33 | density = | melt = | fusibility = | diagnostic = | solubility = | diaphaneity = Translucent, will transmit light on thin edges. | other = | references = }} Gedrite is a silicate mineral of the amphibole group with formula: (Mg;Fe²⁺)₂[(Mg;Fe²⁺)₃Al₂](Si₆Al₂)O₂₂(OH)₂. Gedrite occurs in contact and medium to high grade metamorphic rocks in association with garnet, cordierite, anthophyllite, cummingtonite, sapphirine, sillimanite, kyanite, quartz, staurolite and biotite.

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

References