Multiple oxide containing titanium, 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)
Specific gravity: 4.2 to 5.43
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
Brannerite is among the major uranium-bearing minerals found in ore deposits. It is a
primary mineral in
and in granitic gneiss, in
silicified pebble conglomerates, in hydrothermal quartz and
calcite veins and detrital in placers. Associated minerals include
apatite and zircon
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). Absite occurs in irregular grains in a zone of brecciated rocks ranging from monzogranite to granodiorite (AM 41.166).
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 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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