What is Oskarssonite?
Oskarssonite is a rare iron fluoride associated with fumarolic volcanic environments, where fluorine-rich gases alter hot basaltic rocks.
Mineralogy and crystal structure
Reference formula: Fe3+F3. Oskarssonite is a trigonal iron fluoride and a rare example of fluorine controlling mineral formation at the surface. Natural samples are often tiny and altered. Oskarssonite is classified with halides and has a trigonal crystal system. Typical hardness is 2–3 on the Mohs scale and specific gravity is approximately 3.0–3.2.
Colour, lustre and habit
Typical colours include colourless, white, yellow, brown. The usual tabular, crystalline, massive habit and vitreous, pearly lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Oskarssonite forms in or is associated with fumarolic alteration of basaltic volcanic rocks and fluorine-rich volcanic gas systems. Important documented localities include Hekla and other Icelandic volcanic localities, with related occurrences in volcanic fumaroles.
A fluoride formed by volcanic gas
Oskarssonite captures the chemistry of a fumarole: hot gases move fluorine through fractured lava and produce minerals that could never form in an ordinary sedimentary setting.
Collecting and care
Keep dry, avoid acids and dust, and treat as a specialist research mineral rather than a lapidary material.
