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Formula: Na3Mn2+3Ti2(Si2O7)2(O,OH,F)4
Sorosilicate (Si2O7 groups),
wöhlerite group,
manganese and titanium bearing
mineral
Crystal System: Monoclinic
Specific gravity: 3.6 measured, 3.71 calculated
Hardness: 5
Streak: Light brown
Colour: Reddish brown, golden brown
Common impurities: Ca,Fe,Zr,Nb,Ta,K,H2O
Environments
Plutonic igneous environments
Pegmatites
Localities
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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