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Formula: CaFe3+AlSiO6
Inosilicate (chain silicate), clinopyroxene subgroup,
pyroxene group
Crystal System: Monoclinic
Specific gravity: 3.54 calculated
Hardness: 6
Streak: White
Colour: Red-brown
Common impurities: Ti,Mn,Mg,Na
Environments
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).
Localities
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).
Esseneite from the Durham Ranch - Image
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