Habit: Crystals prismatic to pyramidal, as irregular masses or grains. Typically metamict. Black to brownish-black, brown, gray, yellow. Opaque, transparent on thin edges. Dull, vitreous Luster.
Environment: Typical of rare-earth-bearing Granite Pegmatites; in placers
Etymology: Named for Robert Ferguson (1767-1840) Scottish advocate, politician, mineralogist.