The oxygen atom in the formula might require classification in the Oxides Class of minerals except that the structures are more tied to the halide elements and the oxygens and hydroxides are kind of superfluous to the overall structure. Some other members of the Oxyhalides and Hydroxyhalides include bideauxite , chloroxiphite , kelyanite , blixite , botallackite , laurionite , paralaurionite , mendipite , fiedlerite , pinchite , penfieldite , yedlinite , atacamite , koenenite , cumengite , zirklerite and paratacamite . Of these, only atacamite and boleite are common enough to be seen at rock shows and in rock shops with regularity. Color is sky blue to dark blue. Luster is adamantine.
Crystals are usually translucent to transparent.
Cleavage is perfect. Fracture is conchoidal. Streak is blue. Associated Minerals include other copper and lead minerals such as boleite , linarite , anglesite , wulfenite , phosgenite and cerussite . Notable Occurrences are limited to the Mammoth-St.