Needles of ferro-gedrite on cleavage plane (001) of sekaninaite. Ferrogedrite is a product of weathering and decay of sekaninaite. From: Dolní Bory, Křižanov, Žďár nad Sázavou, Vysočina Region, Czech Republic. — Photo: David Hospital · CC BY-SA 4.0
Ferro-gedrite
The iron end-member of the orthorhombic gedrite amphibole subgroup.
Intro adapted from Wikipedia (CC BY-SA).
Ferro-gedrite is an IMA-recognized mineral species in the silicate class, with the chemical formula Fe²⁺₂(Fe²⁺₃Al₂)(Si₆Al₂)O₂₂(OH)₂.
It crystallizes in the orthorhombic crystal system. It is a member of the Amphibole structural group.
Key properties: Mohs hardness 5.5–6; specific gravity 3.566; [Vitreous.] luster; optically biaxial.
IMA symbol Fged, IMA status: approved, named in 1939.
Found in contact metamorphosed pelitic rocks.
It is found associated with Chamosite, chlorite, andalusite, cordierite, garnet, muscovite, biotite, spinel, quartz, labradorite, magnetite, graphite.
The name refers to ferrous iron in its composition and similarity to gedrite.