Sorosilicate (Si2O7 groups), wöhlerite group, manganese and titanium bearing mineral
Specific gravity: 3.6
Streak: Light brown
Colour: Reddish brown, golden brown
Common impurities: Ca,Fe,Zr,Nb,Ta,K,H2O
Plutonic igneous environments
At the type locality, Gjerdingselva, Lunner, Viken, Norway, there is a mineralogically unique ekerite pluton, with elpidite and kupletskite as rock-forming minerals. The elpidite-bearing area of the ekerite with miarolitic cavities is confined to the western part of the pluton. Janhaugite is widespread, found partly as grains in ekerite and partly in miarolitic cavities as lamellar aggregates and sprays of crystal prisms, to 4 mm long. Janhaugite is often found intimately associated with pyrophanite, or embedded in a fine-grained light-colored elpidite. Other associated minerals include monazite, dalyite, kupletskite, aegirine and a clay-like mixture of montmorillonite and kaolinite (AM 68.1216-1219, Mindat, HOM).
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