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Formula: KZr2(PO4)3
Anhydrous normal phosphate, zirconium-bearing mineral
Crystal System: Trigonal
Specific gravity: 3.194 measured, 3.206 calculated
Hardness: 4½
Streak: White
Colour: Pale blue to pale green to colourless
Luminescence: Nonfluorescent
Solubility:
Common impurities:
Environments
Pegmatites
Hydrothermal environments
Kosnarite is a very rare mineral, formed by late hydrothermal alteration, probably of
beryl and zircon, in complex
granite
pegmatites
(HOM).
Localities
The Wycheproof granite quarry, Wycheproof, Buloke Shire, Victoria, Australia, is in a
granitic
pegmatite where kosnarite, as rhombohedral crystals
to 0.5 mm, is associated with
wycheproofite, eosphorite,
selwynite, cyrilovite and
schorl in a single miarolitic cavity.
Gainesite and several unknowns also occur in the same vein
(HOM, AM 78.653-656).
At the Mario Pinto mine, Taquaral, Itinga, Minas Gerais, Brazil, the
pegmatite is medium-grained, composed dominantly of
muscovite and feldspar with an
irregular quartz core having a maximum thickness of 15 m. Kosnarite is
a secondary hydrothermal mineral that occurs in miarolitic
cavities as beige to pale yellow druses of euhedral, pseudocubic crystals up to 3 mm associated with
albite and sprays of zanazziite
(CM 58.5.637–652).
At the Emmons Quarry, Uncle Tom Mountain, Greenwood, Oxford County, Maine, USA, the Emmons
pegmatite is a highly evolved
granitic
pegmatite. A recent find of several closely associated small
lithiophilite masses to 8 cm across revealed an unusual concentration
of dark brown zircon crystals to 5 mm embedded within the
lithiophilite and associated replacement
hureaulite and rhodochrosite.
The zircon crystals show no evidence of alteration. A few light brown
kosnarite grains were found among the zircon crystals. In one
zircon, a core of kosnarite was discovered that was completely encased
by zircon. The kosnarite shows crystal forms that reach 1.5 mm.
Kosnarite formed almost simultaneously but a little earlier than the
zircon and is therefore not a replacement product of
zircon. This is the first reported occurrence of
primary kosnarite. Chemically, both the
zircon and the kosnarite contain elevated levels of hafnium
R&M 97.6.566
There are two co-type localities, Mount Mica Quarry, Paris, and Black Mountain Quarry, Rumford, both in Oxford county,
Maine, USA.
At Mount Mica Quarry, Paris, Oxford County, Maine, USA, one of the type localities, kosnarite was found in the
granitic
pegmatite in a boulder approximately 1 x 1.3 x 1.7 m in size.
Groundmass minerals of the boulder are albite,
quartz, almandine,
spessartine, muscovite,
siderite and apatite. Embedded in
these groundmass minerals are blue elbaite,
lepidolite, beryl,
montebrasite, rhodochrosite,
cassiterite,
columbite-(Mn), uraninite
and lollingite. Within the mass of the boulder were small vugs (1-5 mm
across) developed in siderite and massive
apatite. These vugs contained euhedral crystals of
siderite, eosphorite,
fluorapatite, moraesite,
quartz and kosnarite. Pseudocubic crystals of kosnarite are as
much as 0.9 mm in size. Other vugs (2-3 mm across) contained euhedral crystals of
albite, quartz,
siderite, eosphorite and
roscherite.
Another new mineral species, the Cs analogue of gainesite, was found in the
vugs associated with quartz, siderite
and albite. Both kosnarite and the Cs analogue of
gainesite formed late in the paragenesis as late-stage hydrothermal
alteration products of earlier formed pegmatite minerals
(AM 78.653-656).
At the Black Mountain Quarry, Rumford, Oxford County, Maine, USA, one of the type localities, kosnarite occurs
in a zoned granitic
pegmatite and is associated with
quartz, albite,
rubellite and lepidolite.
Primary accessory minerals in the
pegmatite include garnet,
columbite-(Mn),
tantalite-(Mn), beryl,
cassiterite and small amounts of
apatite, triphylite,
zircon and pyrite
(AM 78.653-656).
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