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Formula: Mg(C2O4).2H2O
Oxalate, humboldtine group
Crystal System: Monoclinic
Specific gravity: 1.85 measured
Hardness: 2
Streak: White
Colour: White, colourless
Solubility: Soluble in water, easily dissolved by hydrochloric acid
Environments
Biogenic
Glushinskite is a common biomineral formed by reaction between magnesium-rich minerals and oxalic acid
secreted by incrusting lichen
(Webmin).
Localities
At the Lake Huleh Preserve, Northern Jordan Valley, Northern District, Israel, glushinskite occurs in desert
plants.
The saguaro is a cactus that grows to 15 m tall and weighs up to several tons, of which 85% to 90% of the mass
is water. Roughly 18% of the dry mass consists of the biomineral
weddellite, derived from atmospheric carbon dioxide by photosynthesis.
After the death of the saguaro, minerals crystallise in the
rotting flesh, formed from elements released from the decay of the cactus by microorganisms.
During the initial stages of decay, minerals formed include
lansfordite,
nesquehonite, glushinskite,
monohydrocalcite,
calcite and vaterite. Further
decay produces warm, moist pockets within the dead saguaro that contain abundant, glassy
lansfordite crystals to 1 mm in diameter. Then
nesquehonite and
monohydrocalcite crystallise and finally a pale-brown to
tan-coloured sand of weddellite and its transformation product
monohydrocalcite. This
monohydrocalcite further alters to
calcite. Decay of the saguaro adds atmospheric carbon to the soil as
inorganic carbon from the transformation of the biomineral weddellite
to calcite
(AM 88.1879-1888).
At the type locality, the Chai-Tumus coal deposits, Lena River Basin, Bulun District, Polar Yakutia, Sakha
Republic, Russia, glushinskite occurs as veinlets in brown coal seams impregnated with natural acetic acid.
Associated minerals include whewellite,
weddellite, calcite,
dolomite, stepanovite and
zhemchuzhnikovite
(HOM).
At Mill of Johnston, Insch, Aberdeenshire, Scotland, UK, glushinskite occurs at the lichen/rock interface on
serpentinite colonised by the lichen Lecanora atra. It is
formed by reaction between magnesium-rich minerals and oxalic acid secreted by the incrusting lichen, and found in
a creamy white layer intermingled with the filaments of the lichen fungus. The glushinskite consists of
crystals 2 to 5 microns in size with a distorted pyramidal shape, often with curved and striated faces. Associated
minerals include whewellite,
chrysotile and quartz
(AM 66.439, HOM).
Glushinskite from Mill of Johnston - Image
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