Habit: Bright yellow to lemon yellow or slightly greenish. Rarely as crystals, with a diamond-shaped outline; typically fine aggregates or powdery to massive. Dull, earthy; semitransparent. Light yellow streak.
Environment: Occurs in sandstones, typically in paleochannels and in calcretes and near playas. It is an alteration product of uraninite, montroseite or davidite.
Etymology: Named for Marie-Adolphe Carnot (1839-1920), a French mining engineer and chemist.