Heftetjernite
Heftetjernite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula ScTaO₄.
It crystallizes in the monoclinic crystal system (space group P2/c). It is a member of the Wolframite structural group.
Key properties: Mohs hardness 4.5; specific gravity 6.44; Dark brown with a reddish hue streak; Adamantine luster; optically biaxial.
IMA symbol Hef, IMA status: approved, named in 2006.
Found in vugs in albite in a mixed LCT-NYF type cleavelandite-amazonite pegmatite.
It is found associated with Albite, fluorite, muscovite, altered milarite, and a metamict, dark grayish brown mineral of the pyrochlore-microlite group.
The name refers to the locality from which the first specimens were obtained, Heftetjern pegmatite, Norway.