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Formula: KAlSi3O8.H2O
Published without approval
Tectosilicate (framework silicate)
Crystal System: Hexagonal
Environments
K-cymrite is an ultra-high-pressure phase, stable above 2.5 GPa and 600C, and up to 9 GPa at 1200oC. It was
first observed in an experiment as a product of hydration of sanidine.
Crystallisation is possible when approximately equimolar amounts of water are present. When the water amount exceeds that of
the KAlSi3O8 molecule, melting occurs leading to corundum,
kyanite and muscovite.
Common associates include apatite, garnet,
omphacite, orthoclase and
rutile
(Mindat).
Localities
At the Kokchetav Massif, Zerendy, Akmola Region, Kazakhstan (the only validated reported locality),
kokchetavite and K-cymrite occur in association with
phengite,
löllingite, calcite and
α-cristobalite in polyphase mineral inclusions in
clinopyroxene of
calc-silicate ultrahigh-pressure metamorphic rocks. The mode of
occurrence of K-cymrite and kokchetavite in these rocks is strong
evidence for kokchetavite formation through the dehydration of K-cymrite.
The presence of fluid inclusions and K-cymrite in the polyphase mineral inclusions testify for water-saturated
conditions in the rock-forming environment near peak metamorphic conditions
(EJM 25.807-816).
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