Images
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
Environments
Localities
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).
Back to Minerals