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Formula: SrAl3(SO4)(PO4)(OH)6
Compound phosphate, beudantite group,
strontium-bearing mineral, forms a series with
woodhouseite
Crystal System: Trigonal
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).
Svanbergite from Hålsjöberg - Image
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)
At the Tintic Mining District, Utah, USA, good cubic crystals of svanbergite ranging in colour from tannish
cream to pale brown, and generally measuring about 0.2 mm in size, have been found at three the Centennial Eureka,
Trixie and North Star mines. It is found most commonly in the mineralisation containing
tellurium minerals
(MinRec 55.2.223).
Svanbergite from Tintic - Image
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