Color is black with a tint of yellow, brown or green. Luster is earthy to metallic and sometimes vitreous when translucent. Crystals are generally opaque but some translucent specimens are known. Some crystals can be quite large and can weigh up to and slightly over 100 kg. Cleavage is absent.
Fracture is conchoidal.
Extreme variation caused by variable composition of component metals. Streak is yellow to brown. Associated Minerals include quartz , feldspars , columbite , tantalite , zircon , biotite , thorite , allanite , fergusonite and other rare earth minerals. Best Field Indicators are crystal habit, luster, fracture, color, radioactivity, associations, environment and specific gravity.