BOLEITE ON MATRIX, LOOSE CRYSTAL 3.5 mm

Boleite is a rare, complex halide mineral represented by the formula KPb26Ag9Cu24(OH)48Cl62. Initially identified in 1891 as an oxychloride mineral, it crystallizes in deep-blue cubes and belongs to the isometric category. Several related minerals, including pseudoboleite, cumengite, and diaboleite, share its intricate crystal structure and exhibit similar bright-blue cubic forms. These minerals typically form in altered areas of lead and copper deposits, resulting from the interaction of chloride-rich solutions with primary sulfide minerals.

The external characteristics of boleite reveal its cubic crystal structure, placing it within the isometric crystal class. It exhibits perfect cleavage along the [001] direction and displays a very dark glossy blue hue, accompanied by a light greenish-blue streak. Twinning is prominently observed through notches at the interpenetrated angles, leading to a pseudocubic penetration twinning habit at three mutually perpendicular angles. Boleite crystals can reach sizes exceeding half an inch on each side, featuring pseudo-octahedral tetragonal dipyramids.

The crystal on this specimen is approx 3.5 mm.

Former John Betts Collection NY (label attached) #6416