Dmisteinbergite

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Formula: Ca(Al₂Si₂O₈)
Phyllosilicate (sheet silicate), high-temperature, hexagonal paramorph of triclinic anorthite, tetragonal stöfflerite and monoclinic, high-temperature svyatoslavite
Crystal System: Trigonal
Specific gravity: 2.73 measured
Hardness: 6
Streak: White
Colour: Colourless
Common impurities: Mg,Na,K
Environments

Burned coal dumps
Meteorites

Localities

At the Allende meteorite, Pueblito de Allende, Chihuahua, Mexico, dmisteinbergite was identified in a rounded coarse-grained igneous Ca-, Al-rich inclusion from the Allende carbonaceous chondrite. It belongs to a very rare type of refractory inclusions, which experienced melt evapouration and crystallisation at low total gas pressure (P less than 10^-6 bar) in a high-temperature (greater than 1200°C) region, possibly near the proto-Sun (the Sun in the initial stages of its formation, nearly 5 billion years ago), and were subsequently radially transported away from the region, possibly by a disk wind (a particle outflow observed around accretion disks, mainly near protoplanetary disks - Wiki). The Allende dmisteinbergite occurs as irregular single crystals (100–600 microns in size) in contact with gehlenitic melilite and Al-, Ti- diopside, poikilitically (in which small crystals of one mineral occur within crystals of another) enclosing euhedral spinel and rare anorthite. It is colourless and transparent. Dmisteinbergite could have crystallised from a silicate melt at high temperature (~1200–1400°C) via rapid cooling. Dmisteinbergite in Allende, the first find in a meteorite, is a new member of refractory silicates, among the first solid materials formed in the solar nebula. (AM 98.7.1368-1371).

At the type locality, Coal mine No. 45, Kopeysk, Chelyabinsk Oblast, Russia, dmisteinbergite forms hexagonal tablets up to 0.7 mm across on fracture surfaces in blocks from burned coal dumps. Associated minerals include cordierite, mullite, anorthite, wollastonite, tridymite, fayalite, fassaite, norbergite-chondrodite, graphite and iron carbides and monosulphide (AM 77.446-452).

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