Claringbullite
Chemical formula: Cu<sup>2+</sup><sub>4</sub>FCl(OH)<sub>6</sub>
A rare copper mineral characterized by distinctive hexagonal crystals and an intense blue color.
Description
## Characteristics Claringbullite is a rare, secondary copper hydroxyhalide. It forms very characteristic, thin, platy crystals with a perfectly hexagonal outline. They usually occur as small, individual plates or form tiny aggregates, rosettes, and crusts on the surface of the host rock. Its color is intensely blue, from sky blue to turquoise, which makes it easily noticeable despite the small size of the crystals. ## Physical Properties This mineral is relatively soft, with a hardness of about 3 on the Mohs scale. It has a vitreous luster and is transparent to translucent. Its density is quite high, ranging from 3.9 to 4.0 g/cm³, which is typical for copper minerals. ## Colors and Varieties Claringbullite occurs in various shades of blue, most commonly sky blue or blue-green turquoise. The intensity of the color can vary. There are no named color varieties or commercial varieties. ## History and Name The mineral was named in honor of Sir Gordon Frank Claringbull (1911–1990), a British mineralogist and director of the Natural History Museum in London. It was first described from specimens found in the Botallack Mine in Cornwall (United Kingdom). ## Uses Due to its rarity and occurrence in the form of small crystals, claringbullite has no industrial application. It is solely an object of scientific and collecting interest.
Diagnostic features
## Identification The most important diagnostic feature of claringbullite is its habit in the form of perfectly hexagonal, thin plates. The combination of this form with an intense blue color, vitreous luster, and occurrence in association with other secondary copper minerals is usually sufficient for its identification. ## Distinguishing from Similar Minerals Claringbullite is sometimes confused with other blue copper minerals. It is distinguished from connellite by its platy habit (connellite forms acicular crystals), and from spangolite, which can also be platy, by its perfectly hexagonal crystal outline. Botallackite, its polymorph, rarely forms such well-developed crystals. ## Crystal Forms Crystals are in the form of thin, hexagonal plates, often with sharp edges. They can occur individually, but more often form fan-shaped or rosette-like aggregates, as well as small, drusy crusts covering other minerals.
Geological environment
## Genesis Claringbullite is a secondary mineral, formed in the oxidation zones of copper deposits. Its formation requires a specific chemical environment, rich in fluoride and chloride ions. It often crystallizes as a result of the reaction of seawater with old, copper-containing metallurgical slag heaps, as was the case at its type locality. ## Mineral Associations It most often co-occurs with other secondary copper minerals, such as atacamite, paratacamite, botallackite, connellite, as well as malachite and gypsum. ## Localities The most important and historical locality is the Botallack Mine in St Just, Cornwall (United Kingdom). It is also known from ancient slag heaps in Laurion, Greece. Other reported localities include mines in Chile (Atacama) and the USA (Arizona).
Rarity
Very rare
Collector aspects
## Quality Criteria The most highly prized specimens are those with sharp, well-formed, hexagonal crystals of intense, pure blue color. The aesthetic arrangement of crystals on the host rock and association with other rare minerals, creating attractive compositions, is also of great importance, especially for "micromount" specimens. ## Popular Localities Specimens from the type locality in Cornwall are considered classic and have the greatest historical significance. Very good quality microcrystals, often forming impressive rosettes, come from the slag heaps in Laurion, Greece.
Care and storage
## Cleaning Claringbullite specimens are delicate and should be cleaned with great care. It is best to use a soft brush to remove dust. If necessary, the specimen can be briefly rinsed in distilled water and immediately dried with an air stream. Prolonged contact with water should be avoided. ## What to Avoid The mineral is sensitive to chemicals, especially acids, with which it reacts violently. Ultrasonic cleaners, strong detergents, and solvents should be avoided. It is also relatively soft and prone to scratching. It should be protected from high temperatures. ## Storage It is recommended to store specimens in closed containers, such as "micromount" boxes, to protect them from dust, mechanical damage, and potential chemical contamination in the air. It is stable under typical household conditions.