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Formula: NaCaAlF6.H2O
Fluoride, paramorph of
pachnolite
and epitaxial on it.
Crystal System: Monoclinic
Specific gravity: 2.981 measured, 2.986 calculated
Hardness: 2
Streak: White
Colour: Colourless, white, pale lilac; brownish or reddish tinted due to staining; colourless in transmitted light.
Solubility: Readily soluble in sulphuric acid
Environments
Volcanic igneous environments
Pegmatites
Thomsenolite occurs as an alteration product of cryolite and other alkali
aluminum fluorides, most commonly in
granite pegmatites, associated with
cryolite, pachnolite,
hydrokenoralstonite, chiolite,
cryolithionite, elpasolite,
sellaite and fluorite (HOM).
At the type locality, the Ivigtut Cryolite deposit, Sermersooq, Greenland, Denmark, thomsenolite is associated with
pachnolite,
fluorite and
hydrokenoralstonite
(Mindat, Dana).
At the Spider claim, Juab county, Utah, USA, thomsenolite occurs in
rhyolite
associated with tridymite and sodium
boltwoodite (Dana).
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