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Formula: Ca2FeSi2O7
Valence: Ca2Fe2+Si2O7
Sorosilicate (Si2O7 groups), melilite group,
forms a solid solution with gehlenite
Crystal system: Tetragonal
Specific gravity: 3.20 calculated
Hardness: 4½ to 5
Streak: White
Colour: Light yellow
Luminescence: Not fluorescent
Environments
Metamorphic environments
Hydrothermal environments
Localities
At the type locality, the Ferroåkermanite type locality, Hatrurim Basin, Tamar Regional Council, Beersheba
Subdistrict, Southern District, Israel, ferroåkermanite has been found in coarse-grained
kirschsteinite-bearing
paralava. The Hatrurim Basin is one of the largest outcrops of the
Hatrurim Complex composed of high-temperature, low-pressure
metamorphic rocks. It was assumed that these rocks are a
product of combustion metamorphism (pyrometamorphism),
occurring under sanidinite facies conditions.
High-temperature pyrometamorphic rocks are gradually altered by the late hydrothermal and weathering processes,
evidenced by the presence of numerous cavities, veins, and cracks usually filled with low-temperature and
secondary minerals. The presence of rock-forming minerals
such as gehlenite or rankinite
suggests that the paralava formed under high-temperature conditions.
Furthermore, the presence of Fe2+-bearing phases, such as
kirschsteinite, ferroåkermanite,
chromite, ulvöspinel and
bennesherite indicates the reduced conditions.
Rarely, ferroåkermanite forms single subhedral light yellow crystals up to 50 μm in size with a prismatic
habit. The most common are irregular grains, aggregates and intergrowths with
gehlenite, or ferroåkermanite crystals with
perovskite inclusions. Ferroåkermanite is transparent with a
vitreous lustre
(MM 90.2.286-296).
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