Yellow green crystals of the rare mineral cerchiaraite-(Fe) from the TL in Cerchiara mine, Italy. Ex. Erich Laskowski collection (USA). — Photo: David Hospital · CC BY 4.0
Cerchiaraite-(Fe)
Cerchiaraite-(Fe) is an IMA-recognized mineral species in the silicate class, with the chemical formula Ba₄Fe³⁺₄(Si₄O₁₂)O₂(OH)₄Cl₂[Si₂O₃(OH)₄].
It crystallizes in the tetragonal crystal system (space group I4/mmm). It is a member of the Cerchiaraite structural group.
Key properties: Mohs hardness 4.5; specific gravity 3.71; Colorless to tan or pale green-blue streak; Vitreous luster; optically uniaxial.
IMA symbol Ccr-Fe, IMA status: approved, named in 2012.
Developed in small fractures and veinlets within metacherts of an ophiolitic sequence during prehnite-pumpellyite facies metamorphism.
It is found associated with Aegirine, calcite, Mn-bearing diopside (variety schefferite), hematite, K-feldspar, norrishite, quartz (Cerchiara mine); bazirite, diopside, muirite.
The name refers to the analog of cerchiaraite with dominant iron in the octahedral structural site.