Fluorannite
Fluorannite is an IMA-recognized mineral species in the silicate class, with the chemical formula KFe²⁺₃(Si₃Al)O₁₀F₂.
It crystallizes in the monoclinic crystal system (space group C2/m). It is a member of the Mica structural group.
Key properties: specific gravity 3.15–3.2; Gray streak; Submetallic luster; optically biaxial.
IMA symbol Fann, IMA status: approved, named in 1999.
A rock-forming species in the upper part of an A-type granite.
Prefix, fluor, indicates the fluorine analog of annite.
Index entry. This entry combines official IMA/RRUFF species data with published physical-property data — a full written entry hasn’t been published yet.
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