Formula: CaFe3+AlSiO6
Inosilicate (chain silicate), clinopyroxene
Specific gravity: 3.54
Hardness: 6
Streak: White
Colour: Red-brown
Common impurities: Ti,Mn,Mg,Na

Sedimentary environments
Metamorphic environments

Esseneite is a high-temperature, low-pressure, oxidised and quenched crystallisation product derived from fused sediments contiguous to naturally combusted coal seams. Associated minerals include anorthite, melilite, magnetite-hercynite and glass (HOM).


At the type locality, the Durham Ranch paralava occurrence, Reno Junction, Campbell county, Wyoming, USA, esseneite occurs as prismatic crystals 2-8 mm in length with anorthite, melilite solid solutions, magnetite-hercynite solid solutions, and glass within a slaglike crystalline matrix of paralava. Paralava is a fusion product of sediments overlying and associated with naturally combusted coal seams. Minimum formation temperatures of Wyoming paralava are between 1200oC and 1600oC. The high temperature and low pressure, combined with relatively rapid crystallisation, have produced a myriad of lath-shaped anorthite and melilite solid solutions, euhedral magnetite-hercynite spinel group minerals, prismatic pyroxenes, and interstitial glass (AM 72.148-156).

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