Leverettite

Chemical formula: Cu<sup>2+</sup><sub>3</sub>Co<sup>2+</sup>Cl<sub>2</sub>(OH)<sub>6</sub>

Leverettite is a very rare copper and cobalt hydroxychloride, forming microscopic, tabular crystals of an intense blue color.

## Characteristics Leverettite is a very rare mineral from the halide group, specifically a copper and cobalt hydroxychloride. It occurs as extremely small, hexagonal, tabular crystals, not exceeding 50 micrometers. It forms dispersed rosettes or appears as single crystals on the surface of the host rock. Due to its microscopic size, it is a mineral almost exclusively available to specialized micro-collectors. ## Physical Properties Leverettite crystals exhibit an intense blue color and a vitreous luster. They are transparent to translucent. Hardness and density have not been precisely determined due to the small size of the samples, but the hardness is estimated to be around 2 on the Mohs scale. The mineral does not show fluorescence under ultraviolet light. ## History and Name The mineral was named in honor of Peter Leverett (born 1944), an Australian chemist and mineralogist from the University of Western Sydney. He was recognized for his contributions to the study of secondary ore deposits mineralogy, including the description of many new minerals. Leverettite was approved as a new mineral species by the International Mineralogical Association (IMA) in 2012 (IMA2012-050).

Properties

Mohs hardness
2
Luster
Vitreous
Streak
Light blue
Cleavage
Perfect on {0001}
Transparency
Transparent to translucent
Crystal system
Trigonal

Diagnostic features

## Identification Practical identification of leverettite is based on its characteristic appearance under a microscope: hexagonal, tabular crystals of an intense blue color. Its co-occurrence with other rare secondary minerals in the oxidation zone of cobalt-copper deposits is also crucial. Final confirmation requires advanced analytical methods, such as Raman spectroscopy or EDS analysis. ## Distinguishing from similar minerals Leverettite can be confused with other blue, secondary copper minerals. It is distinguished from calumetite by the presence of cobalt in its chemical composition. From other minerals, such as azurite, it is distinguished by its characteristic hexagonal crystal form, which is different in azurite. ## Crystal forms Leverettite forms thin, hexagonal, tabular crystals. These crystals often arrange themselves into small, rosette-like aggregates or occur as single, isolated plates on the rock surface.

Geological environment

## Genesis Leverettite is a secondary mineral that forms in the oxidation zones (gossans) of polymetallic deposits, in this case, copper and cobalt deposits. It forms as a result of reactions of chloride-rich waters with primary ore minerals in a low-temperature and low-pressure environment. ## Mineral associations This mineral co-occurs with other secondary copper and cobalt minerals. In its type locality (Torrecillas mine in Chile), it was found in association with calumetite, atacamite, caracolite, boleite, pseudoboleite, anglesite, hematite, and quartz. ## Localities The only confirmed occurrence of leverettite in the world is its type locality: the Torrecillas mine, located near Salar Grande, in the Iquique Province, Tarapacá Region, Chile.

Rarity

Extremely rare

For collectors

## Quality criteria The quality of a leverettite specimen is assessed solely based on micromount collecting criteria. The most desirable specimens are those with sharply defined, well-formed crystals of an intense blue color, forming aesthetic rosettes. Contrast with the substrate (matrix) and the absence of mechanical damage, which is easily visible under a microscope, are also important. The size of the crystals, even if it refers to tens of micrometers, also increases the value of the specimen. ## Popular localities The only source of leverettite specimens is the Torrecillas mine in Chile. All specimens available on the collector's market come from this single location.

Care and storage

## Cleaning Leverettite specimens, due to their microscopic size and delicacy, generally should not be cleaned mechanically or chemically. Any attempt at cleaning risks irreversible damage or loss of crystals. If absolutely necessary, the specimen can be very carefully blown with compressed air from a safe distance. ## What to avoid Contact with water, acids, detergents, and all chemicals must be strictly avoided. The crystals are extremely fragile and sensitive to shocks and abrasion. They should be protected from dust and moisture. ## Storage Specimens should be stored exclusively in specialized, sealed "micromount" boxes, which protect against dust, moisture, and mechanical damage. Display is only possible under a microscope.

Sources

Read more