The type locality for cliffordite, the San Miguel Mine and other mines of Moctezuma, Sonora, Mexico , is famous for rare telllurium minerals. A class of symmetry that contains the sulfide mineral pyrite , among others. Cliffordite is a radioactive mineral and should be stored away from minerals that are affected by radioactivity and of course human exposure should be limited. Color is bright yellow to sulfur yellow. Luster is adamantine.
Crystals are transparent to translucent.
Crystal Habits include small octahedral crystals. Hardness is 4. Streak is bright yellow. Specimens are slightly radioactive. Associated Minerals include tellurium and other tellurates and tellurites .