Thomsenolite is a mineral with formula: NaCaAlF₆·H₂O. It is an alteration product of

cryolite Cryolite ( Na3 Al F6, sodium hexafluoroaluminate) is an uncommon mineral identified with the once-large deposit at Ivittuut on the west coast of Greenland, mined commercially until 1987. History Cryolite was first described in 1798 by Danish vete ...

.Handbook of Mineralogy
/ref> It was discovered in 1868 in

Ivigtut Ivittuut (formerly, Ivigtût) (Kalaallisut: "Grassy Place") is an abandoned mining town near Cape Desolation in southwestern Greenland, in the modern Sermersooq municipality on the ruins of the former Norse Middle Settlement. Ivittuut is one of ...

Greenland Greenland ( kl, Kalaallit Nunaat, ; da, Grønland, ) is an island country in North America that is part of the Kingdom of Denmark. It is located between the Arctic and Atlantic oceans, east of the Canadian Arctic Archipelago. Greenland is t ...

and named for Hans Peter Jorgen Julius Thomsen (1826–1909).Mindat.org entry
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References

Sodium minerals Calcium minerals Aluminium minerals Fluorine minerals Monoclinic minerals Minerals in space group 14 {{halide-mineral-stub