Ferrogedrite is an amphibole mineral with the complex chemical formula of ☐Fe2+2(Fe2+3Al2)(Si6Al2)O22(OH)2. It is sodium and calcium poor, making it part of the magnesium-iron-manganese-lithium amphibole subgroup. Defined as less than 1.00 apfu (atoms per formula unit) of Na + Ca and consisting of greater than 1.00 apfu of (Mg, Fe2+, Mn2+, Li) separating it from the calcic-sodic amphiboles. It is related to anthophyllite amphibole and gedrite through coupled substitution of (Al, Fe3+) for (Mg, Fe2+, Mn) and Al for Si. and determined by the content of silicon in the standard cell.
{{infobox mineral | name = Ferrogedrite | boxwidth = 300px | image = Ferro-gedrite & Sekaninaite.jpg | imagesize = | alt = | caption = Needles of ferro-gedrite on cleavage plane (001) of sekaninaite. | category = InosilicatesAmphibole | formula = ☐Fe2+2(Fe2+3Al2)(Si6Al2)O22(OH)2 | strunz = 9.DD.05 | dana = | system = Orthorhombic | class = Dipyramidal (mmm)H-M symbol: (2/m 2/m 2/m) | symmetry = Pnma | unit cell = a = 18.52 Å, b = 17.94 Å, c = 5.31 Å; Z = 4 | color = Pale greenish-gray to brown | habit = Crystals prismatic to bladed; fibrous | twinning = | cleavage = Perfect on {210}, with 54° and 126° intersections | fracture = | tenacity = Brittle | mohs = 5.5–6 | luster = Vitreous | streak = Gray white | diaphaneity = Transparent to translucent | gravity = 3.566 | density = | polish = | opticalprop = Biaxial (-) | refractive = nα = 1.642 - 1.694nβ = 1.649 - 1.710nγ = 1.661 - 1.722 | birefringence = δ = 0.019 - 0.028 | pleochroism = X = pale green; Y = brownish green; Z = greenish blue | 2V = Measured: 82° | dispersion = r 2+2(Fe2+3Al2)(Si6Al2)O22(OH)2. It is sodium and calcium poor, making it part of the magnesium-iron-manganese-lithium amphibole subgroup. Defined as less than 1.00 apfu (atoms per formula unit) of Na + Ca and consisting of greater than 1.00 apfu of (Mg, Fe2+, Mn2+, Li) separating it from the calcic-sodic amphiboles. It is related to anthophyllite amphibole and gedrite through coupled substitution of (Al, Fe3+) for (Mg, Fe2+, Mn) and Al for Si. and determined by the content of silicon in the standard cell.
==Occurrence== Specimens of ferrogedrite have been collected in the greenstone belt of Africa, in the mountains of Norway, Greenland, Japan and in amphibole specimens from northwest America as well as the southern coast of California. Ferrogedrite exists in low temperature, high pressure contact metamorphic geologic settings and remain stable up to 600 °C-800 °C due to its iron content.
Discovered by embedding cosine similarity (sentence-transformers MiniLM, 384-dim).