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Formula: BaAl3(PO4)(PO3OH)(OH)6
Hydrated phosphate containing hydroxyl, plumbogummite group,
alunite supergroup, forms a
series with goyazite
Crystal System: Monoclinic
Specific gravity: 3.036 to 3.185 measured, 3.389 calculated
Hardness: 6
Streak: White
Colour: White, colourless, green or brown, may be mottled, colourless in transmitted light
Common impurities: Ca,Ce,Sr
Environments
Pegmatites
Carbonatites
Sedimentary environments
Hydrothermal environments
Gorceixite occurs in
pegmatites, sedimentary phosphate beds, carbonatites,
iron ore deposits, polymetallic veins and
baryte-fluorite veins
(Mindat). It is probably always a secondary mineral
(HOM).
Localities
In the Sydney basin, New South Wales, Australia, gorceixite is associated with
dawsonite, alumohydrocalcite
and nordstrandite
(HOM).
At the Moculta Phosphate Quarry, Angaston, Barossa Valley, North Mt Lofty Ranges, South Australia, gorceixite
is rare and occurs as sprays to 2 cm across of pale grey to yellow crystals in cavities lined with crystals of
fluorapatite. Some of the cavities also contain crystals of
baryte to 1 cm
(AJM 17.1.17).
At the type locality, Ouro Preto, Minas Gerais, Brazil, gorceixite occurs as rounded nodules in sediment
(Mindat).
In the Bauru basin, approximately 2 km south of the town of Santo Iniicio, Paraná State, Brazil, Two fossil bone
fragments were found in a sandstone outcrop. Gorceixite formed
by the alteration of apatite was found in the fossil bones using X-ray powder
diffraction, electron-microprobe analyses and optical microscopy. No convincing evidence was found to indicate a
source of barium and strontium required for the replacement of calcium in the
bone phosphate
(CM 37.945-950).
At the Big Fish River, Dawson mining district, Yukon, Canada, gorceixite is associated with
lazulite, siderite,
limonite and quartz
(HOM).
At the Benallt Mine, Rhiw, Aberdaron, Gwynedd, Wales, UK, gorceixite has been discovered on the mine dumps
in association with fluorapatite and
banalsite. It is
secondary in formation, and probably post-mining in origin,
formed by the alteration of fluorapatite and
banalsite
(M&M 33.59-60)
In Dale county, Alabama, USA, gorceixite has been found in four localities a few miles apart, three localities near
Ariton and one near Dill. The gorceixite is found as irregular nodules up to several inches across, in weathered
outcrops of marl
(AM 43.688-694).
At the Ozark Mine, Silvermine, Fredericktown District, Madison county, Missouri, USA, gorceixite occurs in
tin-tungsten deposits with
fluorite, apatite and
baryte
(Dana).
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