Molinelloite

Chemical formula: Cu<sup>2+</sup>(H<sub>2</sub>O)(OH)V<sup>4+</sup>O(V<sup>5+</sup>O<sub>4</sub>)

Molinelloite is a very rare copper and vanadium mineral, forming microscopic, tabular crystals of an intense blue color.

## Characteristics Molinelloite is a hydrated copper vanadate. It occurs as very small, thin, tabular crystals with a hexagonal outline, rarely exceeding 0.2 mm. These crystals form rosette-like or radial aggregates, as well as thin coatings and crusts on the surface of the host rock. Due to its microscopic size, it is a mineral primarily accessible to specialized collectors. ## Physical Properties Molinelloite crystals are flexible and exhibit strong pleochroism – their color changes depending on the observation direction, from dark blue to almost colorless or pale green. The mineral has a vitreous to pearly luster. Hardness and density have not been precisely determined due to the small size of the crystals. ## Colors and Varieties It is characterized by an intense, dark blue color. No varieties have been distinguished. ## History and Name The mineral was discovered in the Molinello copper mine in Liguria, Italy, from which it derives its name. It was approved by the International Mineralogical Association (IMA) in 2013 under number 2013-082. It was first described by G.L. Cinzia, G. Dalla Ventura, F. Castellaro, and G.B. Andreozzi. ## Uses Molinelloite has no industrial application. It is solely an object of scientific interest and a valuable acquisition for collectors specializing in rare minerals or minerals from specific localities (so-called "locality collectors").

Properties

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

Diagnostic features

## Identification Identifying molinelloite under amateur conditions is practically impossible. Identification requires advanced analytical methods, such as Raman spectroscopy or chemical analysis using an electron microprobe (EDS/WDS). A visual feature that may suggest the presence of this mineral is the characteristic, microscopic, hexagonal, blue crystals in the form of rosette-like clusters on the host rock, originating from the type locality. ## Distinguishing from Similar Minerals Molinelloite can be confused with other rare, secondary copper and vanadium minerals of blue color, such as mcalpineite, which also crystallizes in the hexagonal system. Definitive differentiation is possible only based on detailed chemical and crystallographic analysis. ## Crystal Forms The mineral forms thin, tabular crystals with a hexagonal outline. These crystals often combine into radial or rosette-like aggregates, and also form thin coatings on rock surfaces.

Geological environment

## Genesis Molinelloite is a secondary mineral, forming in the oxidation zones of copper deposits. It forms as a result of the weathering of primary ore minerals in the presence of vanadium-rich solutions. At the type locality (Molinello mine), it formed on the surface of basalt. ## Mineral Associations It co-occurs with other secondary copper and vanadium minerals. At the Molinello mine, it was found in association with minerals such as volborthite, tangeite, vesignieite, mcalpineite, goethite, malachite, as well as minerals from the zeolite group. ## Localities The only confirmed and described locality of molinelloite in the world is its place of discovery – the Molinello copper mine, located in the Graveglia Valley, near the town of Ne, in the Liguria region of Italy.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a molinelloite specimen is primarily assessed based on the richness and development of the crystals. The most prized specimens are those with clearly formed, rosette-like aggregates of intense blue color, contrasting well with the host rock. Due to the microscopic nature of the mineral, the aesthetics of the entire cluster visible under magnification is crucial. The presence of rare associated minerals also increases the value of the specimen. ## Popular Localities The only source of collector specimens is the type locality – the Molinello mine in Italy. Material from this location is extremely rare and sought after by specialized collectors of systematic minerals and micromounts.

Care and storage

## Cleaning Molinelloite specimens are extremely delicate due to their microscopic size and mode of occurrence (coatings, fine aggregates). Mechanical cleaning is not recommended. If absolutely necessary, compressed air can be used from a safe distance to remove dust. Contact with water and any chemicals should be avoided. ## What to Avoid Avoid ultrasonics, steam cleaners, acids, solvents, and detergents. The mineral is sensitive to chemical and physical action. Protect it from high temperatures and humidity. ## Storage It is recommended to store specimens exclusively in specialized, sealed "micromount" boxes, which protect them from dust, mechanical damage, and sudden changes in humidity. Exposure should be away from direct sunlight and heat sources.

Sources

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