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
Common impurities:

Hydrothermal environments

Kosnarite is a very rare mineral, formed by late hydrothermal alteration, probably of beryl and zircon, in complex granite pegmatites (HOM).


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).

Back to Minerals