Overview
Claringbullite is a rare blue copper halide-hydroxide mineral that forms in the oxidised zones of copper deposits and, occasionally, in copper-bearing slags. Its delicate blue colour and scarcity make it a prized micromount and specialist collector species, though good crystals are uncommon. It is best known to mineralogists as the structural cousin of barlowite and as a member of a small group of copper oxysalt minerals studied for their unusual magnetic properties.
Composition & structure
Claringbullite is a hydrated copper chloride-fluoride hydroxide. It was originally described with a chloride-dominant formula, and refined study established essential fluorine, giving the modern formula Cu4FCl(OH)6. The structure is built from sheets of copper-oxygen-hydroxyl polyhedra with chlorine and fluorine in the interlayer, and it is isostructural with the bromine analogue barlowite. It crystallises with hexagonal symmetry and shows a characteristic light to deep blue colour.
| Formula | Cu4FCl(OH)6 |
| Crystal system | Hexagonal |
| Mohs hardness | Soft (a delicate copper oxysalt) |
| Lustre | Vitreous to pearly |
| Colour | Blue to light blue |
| Type locality | Bisbee, Cochise County, Arizona, USA |
Formation & occurrence
Claringbullite is a secondary mineral, forming where primary copper sulphides weather in the presence of chlorine-rich and fluorine-bearing solutions. Such conditions arise in the oxidised caps of copper orebodies and in altered copper-rich slags. It typically occurs with other secondary copper minerals such as atacamite, malachite and connellite, growing as tiny tabular or platy crystals and crusts on fracture surfaces.
Identification & similar species
The blue colour invites confusion with commoner copper minerals. Claringbullite can resemble the copper chloride atacamite and other blue secondary species, and reliable distinction depends on crystallography and chemical analysis rather than appearance alone. Its hexagonal habit and close structural relationship to barlowite are diagnostic to specialists, but in hand specimen it is essentially indistinguishable from several associated copper oxysalts without instrumental study.
Notable localities & collecting
The type locality is Bisbee, Arizona, in the United States. Among the most rewarding localities for collectors is the famous Mina Ojuela at Mapimi, Durango, Mexico, which has produced some of the finest material. Additional occurrences are documented at copper deposits and slag sites in several countries. Because crystals are minute and the species is scarce, claringbullite is a micromineral of interest mainly to advanced collectors and researchers rather than a showpiece for display.