Ferriallanite-(La)
Ferriallanite-(La) is an IMA-recognized mineral species in the silicate class, with the chemical formula CaLa(Fe³⁺AlFe²⁺)[Si₂O₇][SiO₄]O(OH).
It crystallizes in the monoclinic crystal system (space group P2_1/m). It is a member of the Epidote, allanite structural group.
Key properties: Mohs hardness 6; specific gravity 4.099; Brown streak; Vitreous luster; optically biaxial.
IMA symbol Faln-La, IMA status: approved, named in 2010.
Found in a void in a sanidinite xenolith in pumice.
It is found associated with Sanidine, ‘biotite’, magnetite, nosean, clinopyroxene.
The suffix identifies the La-analogue of ferriallanite-(Ce). Honors Thomas Allan (1777- 1833), Scottish mineralogist who discovered the species. The prefix, ferri, indicates Fe3+ > Al.
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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