Esseneite

Esseneite is a relative rare mineral of the pyroxene group, with formula CaFeAlSiO₆. It is the ferric-iron-dominant member. Esseneite is an iron-analogue of other pyroxene-group members, davisite, grossmanite, and kushiroite. It is a metamorphic mineral forming in pyrometamorphic rocks called paralavas, which are formed due to fusing on sedimentary rocks usually in result of coal fires. Esseneite is found in both natural and anthropogenic coal-fire sites.^[1][2]

Esseneite
Reddish-brown dorrite crystals associated to orange essenite, and also spinel and magnesioferrite. From: Chelyabinsk, Chelyabinsk Oblast, Russian Federation
General
Category	Minerals
Formula	CaFeAlSiO6
Crystal class	Monoclinic – prismatic
Identification
Color	Reddish brown
Cleavage	110 – Perfect
Luster	Vitreous (glassy)
Streak	White
Diaphaneity	Transparent
Density	3.54

Esseneite was named for Eric J. Essene (1939–2011), a metamorphic petrologist and Professor of Geosciences at the University of Michigan.

The mineral crystallizes in the monoclinic crystal system with space group C2/c.^[1]