Ferriakasakaite-(La) and ferriandrosite-(La) crystal. These two minerals are visually indistinguishable, and are also identical in appearance as vanadoallanite-(La). In fact, ferriakasakaite-(La) and ferriandorosite-(La) were identified during an attempt to identify more vanadoallanite-(La) for further studies. All three minerals are found in the same rhodochrosite/tephroite veins in a ferromanganian ore. The photo is from the type material and is taken by Dr. Daisuke Nishio-Hamane, one of the co-authors of the species. — Photo: Dr. Daisuke Nishio-Hamane · CC BY 3.0
Ferriandrosite-(La)
Ferriandrosite-(La) is an IMA-recognized mineral species in the silicate class, with the chemical formula MnLaFe³⁺AlMn²⁺(Si₂O₇)(SiO₄)O(OH).
It crystallizes in the monoclinic crystal system (space group P2_1/m). It is a member of the Epidote structural group.
Key properties: specific gravity 4.23; Vitreous luster.
IMA symbol Fea-La, IMA status: approved, named in 2013.
Found in tephroite-calcite veinlets cutting a stratiform ferromanganese deposit.
It is found associated with Ferriakasakaite-(La), rhodochrosite, bementite, allanite-group minerals.
The name refers to a member of the allanite group with dominant Mn2+ in the A1 site and Fe3+ in the M1 site, and a suffix for the dominant rare earth element.