Brownmillerite

brownmillerite

portlandite

melilite

kalsilite

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Formula: Ca₂Fe³⁺AlO₅
Multiple oxide, brownmillerite subgroup, perovskite supergroup, forms a series srebrodolskite
Crystal System: Orthorhombic
Specific gravity: 3.76 measured, 3.70 calculated
Streak: Light brown
Colour: Reddish brown
Environments

Metamorphic environments

Brownmillerite occurs in thermally metamorphosed limestone blocks included in volcanic rocks (Webmin)

Localities

At Klöch, Südoststeiermark District, Styria, Austria, is associated with melilite, mayenite, wollastonite, kalsilite and corundum (HOM ).

Brownmillerite has two co-type localities, the Ettringer Feld and the Mayener Feld, both at the Southern lava flow, Bellerberg volcano, Ettringen, Mayen, Mayen-Koblenz, Rhineland-Palatinate, Germany. Here it occurs in thermally metamorphosed limestone blocks included in volcanic rocks, associated with calcite, ettringite, wollastonite, larnite, mayenite, gehlenite, diopside, pyrrhotite, hydrocalumite, grossular, spinel, chlormayenite, afwillite, jennite, portlandite and jasmundite (AM 50.2106, HOM, Mindat, Dana).

At the Hatrurim formation, Israel, occurs in high-temperature, thermally metamorphosed, impure limestone associated with spurrite, larnite and mayenite (HOM)

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