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Formula: SrB2Si2O8
Tectosilicate (framework silicate), strontium- and
boron- bearing mineral
Crystal System: Orthorhombic
Specific gravity: 3.35 measured, 3.36 calculated
Hardness: 6½ to 7
Streak: White
Colour: White, colourless
Environments
Pekovite was approved in 2003 but to date (April 2025) it has been reported only from the type locality.
Localities
At the type locality, the Dara-i-Pioz Massif, Districts of Republican Subordination, Tajikistan,
a glacier descends from the southern slope of the Igla Mountain, which is situated at the intersection of
the Turkestan, Alai and Zeravshan mountain ranges, and fragments of alkaline rocks and
pegmatites of the massif occur in the moraine of the glacier.
The massif is known for very high contents of boron, hence a widespread and
varied occurrence of boron minerals, including
tienshanite,
tadzhikite-(Ce),
kapitsaite-(Y), maleevite
and pekovite that were first described from this massif.
Pekovite was found in a block of quartz. The blocks are rounded and
vary from 0.2 to 2.0 m across; they could be fragments of quartz cores of
pegmatites or fragments of veins. They consist mainly of
medium- to coarse- grained granulated quartz with disseminated large plates
of polylithionite, crystals of
microcline, pockets of pale yellow to pink
reedmergnerite, randomly distributed, usually idiomorphic and almost
black aegirine crystals, rare lenticular crystals of
stillwellite-(Ce), grass-green crystals of
leucosphenite, purple-pink plates of
sogdianite, dark green elongate prismatic crystals of
turkestanite with a high content of U4+ and H2O,
and polymineralic pockets lined mainly by pectolite.
Galena, calcite,
kapitsaite-(Y), neptunite,
sugilite, pyrochlore,
eudialyte group minerals,
tadzhikite-(Ce), baratovite,
native bismuth, sphalerite,
fluorite, fluorapatite,
fluorapophyllite,
zeravshanite and several unknown
cesium-bearing minerals are less abundant in the
quartz blocks. Pekovite occurs as anhedral equant grains from 0.05 to
0.2 mm, commonly intergrown with pectolite,
quartz, highly strontian
fluorite and aegirine
(CM 42.1.107-119).
Pekovite from the Dara-i-Pioz Massif -
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