Ramaccioniite

Chemical formula: Cu<sup>2+</sup><sub>4</sub>[Se<sup>6+</sup>O<sub>4</sub>](OH)<sub>6</sub>

Ramaccioniite is a very rare copper hydroxyselenate, forming characteristic blue-green, tabular crystals.

## Characteristics Ramaccioniite is a secondary copper and selenium mineral, occurring as very small, tabular or bladed crystals, rarely exceeding 0.2 mm. These crystals form rosette-like or radial aggregates, as well as thin coatings and crusts. Its characteristic, vivid blue-green color makes it recognizable despite its small size. ## Physical Properties This mineral is characterized by a vitreous luster and is transparent to translucent. Due to the microscopic size of the crystals, hardness has not been precisely measured, but it is estimated to be around 3-4 on the Mohs scale. The density calculated based on the chemical formula and unit cell parameters is 4.11 g/cm³. ## Colors and Varieties Ramaccioniite occurs in a uniform, blue-green color. No color varieties or commercial varieties are known. ## History and Name The mineral was discovered in the Baccu Locci copper and uranium mine in the Sarrabus-Gerrei region of Sardinia, Italy. It was approved by the International Mineralogical Association (IMA) in 2014. Its name honors the Italian mineral collector, Pierfranco Ramaccioni (born 1941), for his contribution to the study of Sardinian mineralogy and the discovery of many new minerals. ## Uses Ramaccioniite has no industrial application. Its significance is purely scientific and collectible due to its extreme rarity and status as a new mineral.

Properties

Mohs hardness
3-4
Luster
Vitreous
Streak
Light blue
Density
4.11
Cleavage
Perfect on {001}
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Monoclinic

Diagnostic features

## Identification Ramaccioniite can be identified by its characteristic blue-green color, tabular crystal habit, and formation of rosette-like aggregates. It occurs in the oxidation zones of selenium and copper deposits. Final identification requires advanced analytical methods, such as Raman spectroscopy or X-ray diffraction. ## Distinguishing from Similar Minerals It can be confused with other secondary copper minerals of similar color, such as brochantite, malachite, or other copper selenates (e.g., olsacherite, schmiederite). It is distinguished by its specific form of thin, tabular crystals grouped into rosettes and its co-occurrence with other rare selenites and selenates. ## Crystal Forms Crystals are thin, tabular, with a hexagonal outline, often elongated and bladed. They typically form radial or rosette-like aggregates, as well as thin coatings on the host rock.

Geological environment

## Genesis It is a secondary mineral, formed in the oxidation (weathering) zone of hydrothermal ore deposits rich in selenium and copper. It forms as a result of surface waters acting on primary sulfides and selenides. ## Mineral Associations Ramaccioniite co-occurs with other secondary copper, selenium, and lead minerals. At its type locality (Baccu Locci), it was found in association with anglesite, as well as rare selenites and selenates, such as chalcomenite, schmiederite, olsacherite, and genplesite. ## Localities The only confirmed occurrence of ramaccioniite in the world is its type locality – the Baccu Locci mine, Sarrabus-Gerrei, Sardinia, Italy.

Rarity

Extremely rare

For collectors

## Quality Criteria The most valued specimens are those with clearly formed, sharp crystals creating aesthetic, rosette-like aggregates on a contrasting rock matrix. Due to their microscopic size, the quality of the crystals visible under magnification is crucial. The size of the aggregates and the abundance of occurrence on the specimen also increase its value. ## Popular Localities The only source of specimens is the Baccu Locci mine in Sardinia, which makes every specimen from this locality extremely desirable for specialized collectors of rare minerals and micromounts.

Care and storage

## Cleaning Specimens should only be cleaned very carefully, using compressed air to remove dust. Due to the mineral's delicacy and reactivity, contact with water and any chemical agents should be avoided. ## What to Avoid Contact with water, acids, detergents, and other liquids must be strictly avoided. The crystals are very brittle and susceptible to mechanical damage. Specimens should not be subjected to ultrasonic cleaning or high temperatures. ## Storage It is recommended to store specimens in sealed, closed "micromount" boxes, protecting them from dust, moisture, and physical damage. Avoid exposure to direct sunlight and humidity changes.

Sources

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