Formula: SiFe2O4
Nesosilicate (insular SiO4 groups), isometric paramorph of orthorhombic asimowite and fayalite, which is also orthorhombic; ulvöspinel subgroup, oxyspinel group, spinel supergroup
Crystal System: Isometric
Specific gravity: 4.135 calculated
Colour: Bluish green



At the type locality, the Tissint Martian meteorite, Tata Cercle, Tata Province, Souss-Massa Region, Morocco, ahrensite has been formed from the transformation of fayalite-rich rims of olivine megacrysts or iron-rich microphenocrysts in contact with shock melt pockets in the olivine-phyric (few phenocrysts) shergottite meteorite. Associated minerals include bridgmanite, ringwoodite, wüstite, stishovite, olivine and ilmenite (HOM).

At the Zagami Martian meteorite, Faskari, Katsina, Nigeria, two high-pressure minerals, tuite and ahrensite, were reported located in two small shock-induced melt pockets in the meteorite, coexisting with granular and acicular stishovite and seifertite. Nanocrystalline ahrensite in a pyroxene clast is likely to be a decomposition product of pigeonite under high pressure and temperature conditions by a solid-state transformation mechanism. The pressure and temperature conditions estimated in the shock-induced melt pockets are ~12–22 GPa and ~1100–1500°C, respectively, although previous estimates of peak shock pressure are higher (AM 107.6.1018–1029).

At the Khatyrka meteorite, Iomrautvaam massif, Anadyrsky District, Chukotka Autonomous Okrug, Russia, the meteoritic grain contains evidence of a heterogeneous distribution of pressures and temperatures that occurred during impact shock, in which some portions of the meteorite reached at least 5 GPa and 1200°C. Decagonite is associated with aluminium-bearing trevorite, diopside, forsterite, ahrensite, clinoenstatite, nepheline, coesite, pentlandite, copper-bearing troilite, icosahedrite, khatyrkite, taenite, aluminium-bearing taenite and steinhardtite (AM 100.10.2340-2343).

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