Svanbergite

svanbergite

woodhouseite

pyrophyllite

alunite

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Formula: SrAl3(SO4)(PO4)(OH)6
Compound phosphate, beudantite group, strontium-bearing mineral, forms a series with woodhouseite
Specific gravity: 3.2 to 3.24 measured
Hardness: 5
Streak: White
Colour: Colourless, yellow, reddish brown to rose-pink; colourless in transmitted light
Solubility: Insoluble in acids
Environments

Metamorphic environments
Hydrothermal environments

Svanbergite occurs in aluminous medium-grade metamorphic deposits, in bauxite deposits, and as a secondary product of sulphatic argillic wall-rock alteration in hydrothermal vein and disseminated ore deposits, replacing apatite. Associated minerals include pyrophyllite, kyanite, andalusite, lazulite, augelite, alunite, kaolinite and quartz (HOM).

Localities

At La Escondida Mine, Escondida, El Loa Province, Antofagasta, Chile, aluminium-phosphate-sulphate minerals (APS minerals) are probably of both hypogene and supergene origin. The probable hypogene occurence consists of grains 5 to 50 microns in size, intermediate in composition between svanbergite and woodhouseite, and intergrown with diaspore. An extensive zone of hypogene alunite-pyrophyllite-diaspore alteration is spatially associated with the APS minerals on a broad scale, but no grain contacts between pyrophyllite or alunite and the APS minerals have been observed. In contrast, several finer-grained occurrences of APS minerals at La Escondida are considered to be of supergene origin. Cryptocrystalline material intermediate in composition between woodhouseite and svanbergite fills late fractures and occupies more than 30% of some fist-sized core samples. Fine-grained APS minerals in the zone of supergene copper enrichment are associated with supergene copper sulphides (mainly a fine-grained mixture of djurleite, digenite and anilite), which rim and replace hypogene sulphide grains (CM 25.205).

At the type locality, Hålsjöberg, Torsby, Värmland County, Sweden, svanbergite occurs as euhedral crystals in quartzite, associated with quartz, pyrophyllite and kyanite (Mindat).

At the Summitville Mining District, Rio Grande County, Colorado, USA, aluminum phosphate-sulfate minerals (APS minerals) are common, but occur in only minor amounts. They range in composition from nearly pure Sr to high-Ca varieties, and occur over a depth range of 800 metres. Hinsdalite also occurs locally in the deposit.
The APS minerals occur outside the zone of most intense alteration and mineralisation. This innermost zone is the result of intense hypogene acidsulphate attack, which has removed coarse K-feldspar phenocrysts, leaving a nearly monomineralic quartz rock crowded with coarse voids. Adjacent to this zone, a rock containing predominantly quartz and alunite, with minor kaolinite, forms a 1- to 2- metre halo, with kaolinite more abundant than alunite beyond this distance. At greater depth, kaolinite becomes more abundant or entirely supplants alunite in the interior zone of alteration.
APS minerals occur in the quartz-alunite and quartz-kaolinite zones here. Where associated with alunite, the APS minerals occur as 2.0- to 60- micron pseudocubic grains generally enclosed by alunite. In the quartz-kaolinite zone, the APS minerals occur in clusters of 10- to 30- micron pseudocubes, scattered in inegularly shaped 0.2- to 0.5- mm patches of fine-grained kaolinite. In both zones pyrite is a common accessory mineral, and covellite occurs in trace amounts. APS minerals in these two zones are rich in the svanbergite component but show considerable compositional variability (CM 25.204).

At the Dover claim, Fitting Mining District, Mineral county, Nevada, USA, svanbergite occurs in well formed crystals imbedded in, or emplanted on, green pyrophyllite. The pyrophyllite is abundant in the andalusite-corundum ore, which has been mined periodically and in small quantities (AM 34.104-108)

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