Brannerite Locality: Dieresis Mine, El Cabril, Sierra Albarrana, Hornachuelos , Córdoba , Andalusia , Spain ( Locality at mindat.org ) This is a huge, amazingly symmetrical and complete-all-around crystal of a very rare complex uranium oxide! I think it is a very significant specimen! 6.1 x 4.2 x 3.7 cm — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Brannerite
A uranium-titanium oxide mineral named for geologist John Casper Branner.
Intro adapted from Wikipedia (CC BY-SA).
Brannerite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula UTi₂O₆.
It crystallizes in the monoclinic crystal system (space group C2/m). It is a member of the Brannerite structural group.
Key properties: Dark greenish brown to yellowish brown streak; Pitchlike to vitreous when fresh, resinous to dull when altered luster.
IMA symbol Bnr, IMA status: approved, named in 1920.
Found as a primary mineral in granite pegmatite and in granitic gneiss; in silicified pebble conglomerates; in hydrothermal quartz and calcite veins; detrital in placers.
It is found associated with Uraninite, gold, rutile, xenotime, apatite, zircon.
The mineral was named to honor Dr. John Casper Branner (1850-1922), American geologist, formerly Professor of Geology and President of Stanford University, Palo Alto, California, USA.