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Formula: UTi2O6
Multiple oxide containing titanium and
uranium, monoclinic
paramorph of
orthobrannerite,
which is orthorhombic, forms a series with thorutite
Absite is a a variety of brannerite containing around 12.7% ThO2 (Mindat)
Crystal System: Monoclinic
Specific gravity: 4.2 to 5.43 measured, 5.2 calculated
Hardness: 4½ to 5½
Streak: Dark greenish brown to yellowish brown
Colour: Black, brownish olive-green, yellow-brown to yellow with alteration, yellowish green in transmitted light
Solubility: Decomposed by hot concentrated sulphuric acid (Dana)
Common impurities: Ba,Fe,Pb,REE,Si,Sr,Th,Zr
RADIOACTIVE and metamict
Environments
Pegmatites
Metamorphic environments
Placer deposits
Hydrothermal environments
Brannerite is among the major uranium-bearing minerals found in ore
deposits. It is a
primary mineral in
granite
pegmatites
and in granitic gneiss,
in silicified pebble conglomerates, in hydrothermal quartz and
calcite veins and detrital in placers. Associated minerals include
uraninite, gold,
rutile, xenotime,
apatite and zircon
(HOM).
Localities
At the Nichol Nob Mine, Nichol Nob, Mount Lyndhurst station, North Flinders Ranges, Flinders Ranges, South Australia,
brannerite occurs with uraninite in
calcite veins
(Dana).
At Crocker Well, Mt Victor Plumbago Station, Olary Province, South Australia, brannerite occurs in
quartz veins with rutile,
xenotime, apatite and
zircon
(Dana).
The variety Absite occurs in irregular grains in a zone of
brecciated
rocks ranging from monzogranite to
granodiorite
(AM 41.166).
Brannerite from Crocker Well - Image
The Olympic Dam Mine, Roxby Downs, Stuart Shelf, South Australia, is an iron-oxide,
copper, gold,
silver, uranium deposit that contains three dominant uranium minerals,
uraninite, coffinite and
brannerite. Some brannerite contains inclusions of galena.
Brannerite and coffinite probably precipitated as part of a
late-stage hydrothermal event. Coffinite is often found on the edge of
brannerite
aggregates, suggesting that brannerite precipitated before coffinite
(MM 81.6.1323-1366).
At the Richardson Mine, Madoc Township, Madoc area, Hastings County, Ontario, Canada, the first association in Canada of
brannerite and native gold was recognised, and it is one of the few such
localities in the world. Two brannerite-gold bearing specimens were found,
composed of slightly pinkish, crystalline calcite with
muscovite, brannerite,
tourmaline, pyrite, native
gold and minor uraninite.
Brannerite occurs as discrete black grains and as irregular masses up to 1.2 cm. Native
gold occurs macroscopically in both specimens and is almost invariably
associated with the brannerite, although small grains are isolated in the
calcite. Uraninite is a minor
constituent associated with and, in part, veining the brannerite
(CM12.360-363).
The Pele mountain deposit in the Elliot Lake area, Algoma District, Ontario, Canada, is a
quartz-pebble conglomerate uranium deposit, where the dominant uranium minerals are
thorite and brannerite, with the brannerite
replacing rutile
(AM 97.1274-1283).
At the Zimná Voda uranium occurrence, Prakovce, Gelnica District, Košice Region, Slovakia, a hydrothermal
quartz vein with rare earth element -
uranium - gold mineralisation is
associated with contact metamorphism between
granite and host
phyllite and
metaquartzite. It contains unique rare earth element minerals of
the monazite and xenotime groups.
The middle rare earth element-rich (rich in samarium, europium or gadolinium)
monazites, xenotimes and
hingganite-(Y) precipitated in response to the
alteration of primary
uraninite, brannerite and
fluorapatite by low-temperature hydrothermal fluids. These are
responsible for the strong enrichment of individual medium rare earth elements, especially gadolinium, in the
secondary minerals
(AM 108.754–768).
Brannerite from Zimná Voda - Image
At the Red Boulder No. 1 prospect, One Hole Spring, Bighorn Mountains, San Bernardino county, California, USA,
brannerite forms nodules up to 2 inches across in granite
gneiss. Some of the nodules are embedded in the
gneiss and are surrounded by a thin layer of
biotite, and some are embedded in larger nodules of fresh or altered
biotite. In general, the smaller nodules seem to be wholly brannerite;
the larger nodules contain grains of rutile as large as grains of rice, and in
some cases it appears that brannerite has replaced biotite. Sodic
plagioclase and rutile are
present in
some of the nodules of brannerite
(AM 42.30-38).
At the type locality, Kelley Gulch, Stanley, Stanley Basin Mining District, Custer county, Idaho, USA,
brannerite is found in gold placers near
granite cut
by a pegmatite
(AM 5.105). Associated minerals include zircon,
xenotime-(Y), uraninite,
rutile, gold and
apatite
(Mindat).
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