Grossmanite

grossmanite

spinel

perovskite

melilite

Images

Formula: Ca(Ti³⁺,Mg,Ti⁴⁺)AlSiO₆
Inosilicate (chain silicate), single chains, clinopyroxene subgroup, pyroxene group, titanium-bearing mineral
Crystal System: Monoclinic
Specific gravity: 3.41 calculated for the empirical formula
Colour: Light grey
Luminescence: Non-fluorescent under the beams of the electron microprobe and SEM
Environments

Meteorites

Localities

At the type locality, the Allende meteorite, Pueblito de Allende, Chihuahua, Mexico, micrometer-sized grossmanite occurs with spinel and perovskite in a melilite host in a calcium–aluminium-rich inclusion fragment from the meteorite. This fragment is 330 × 385 µm in the section plane, surrounded by a matrix of mostly olivine and troilite. The Allende meteorite, which fell on February 8, 1969, is a carbonaceous chondrite. Grossmanite is also observed in another calcium–aluminium-rich inclusion, occurring with spinel, perovskite and grossite in melilite near the rim. The type material (1 to 7 µm in size) appears to coat spinel grains. In thin section, it is transparent with a light grey colour that may be caused by adjacent and underlying phases (AM 94.10.1491-1494.
Grossmanite was likely formed through high-temperature condensation in the solar nebula, followed by melting and crystallisation in calcium- and aluminium-rich refractory inclusions in the meteorite (HOM).
Grossmanite from the Allende Meteorite - Image

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