Class : Halides
    Subclass : Fluorides
    Crystal system : Monoclinic
    Chemistry : NaCaAlF₆ H₂O
    Rarity : Rare

Thomsenolite is a dimorphic fluoride of pachnolite, which occurs mainly in granitic pegmatites, sometimes in rhyolites or in fluorinated pegmatites. It is always a secondary mineral formed by alteration of other fluorides. It was named in honor of Hans Peter Jörgen Thomsen, Professor of Chemistry at the University of Copenhagen and pioneer of the industrial exploitation of cryolite in Greenland. Thomsenolite occurs as prismatic crystals up to 5 cm, often grouped in parallel groups, rarely in pseudocubic individuals, stalactites, spherulites or masses of chalcedony appearance. Thomsenolite is colorless or white, but sometimes reddish or pink due to the inclusion of iron oxides.

Main photo : Thomsenolite from Ivigtut, Greenland © Beppe Finello

No known twin for this mineral species. However, some epitaxies can produce crosses.

No fakes listed for this mineral species.