The Mineral BRANNERITE

Chemical Formula: (U⁴⁺,Ca)(Ti,Fe³⁺)2O6 , Uranium Calcium Titanium Iron Oxide
Class: Oxides and Hydroxides
Uses: a major ore of uranium and radium, a source of helium and as a mineral specimen
Specimens

Brannerite is a highly radioactive and interesting mineral. It is named after Dr. John Casper Branner (1850-1922), formerly a Professor of Geology and President of Stanford University.

Brannerite is found in the same settings as gold, including placers, quartz veins, and in granite pematities. It may be black, but is more often found in shades of yellow to brown to green. It forms only tiny crystals, which may be vitreous. Thin sections are translucent, transmitting a yellow-green light. It may fluoresce yellow under short-wave ultra-violet light.

It is one end of a series called the Brannerite-Thorutite series.

PHYSICAL CHARACTERISTICS:

Color is brown in shades of yellow to green; may be yellow or yellow-green in thin sections.
Luster is vitreous, sometimes reported as resinous or dull.
Transparency crystals are translucent.
Crystal System is monoclinic, 2/m
Crystal Habit is prismatic.
Cleavage is absent.
Fracture is conchoidal.
Hardness is 4.5 - 5.5
Specific Gravity is 5.2
Streak is dark greenish-brown to yellowish-brown.
Associated Minerals include gold.
Other Characteristics: radioactive, fluorescent yellow
Notable Occurences include Ontario, Canada; Colorado, Stanley Basin, Wyoming, and Custer County, Idaho, USA (the type locality).
Best Field Indicators are luster, color, radioactivity and streak.