Marioantofilliite

Chemical formula: [Cu²⁺₄Al₂(OH)₁₂](CO₃)(H₂O)₃

Marioantofilliite is a very rare, blue or green mineral from the hydrotalcite supergroup, forming small, platy crystals.

## Characteristics Marioantofilliite is a secondary copper and aluminum mineral belonging to the hydrotalcite supergroup. It occurs as small, hexagonal or pseudohexagonal platy crystals, which typically form rosette-like or spherical aggregates. Crystals rarely exceed 0.2 mm in diameter. Due to its chemical composition and structure, it is closely related to other minerals from this group, such as carbotronite. ## Physical Properties The mineral is characterized by low hardness. The luster is most likely vitreous or pearly on cleavage surfaces, which is typical for minerals with a similar structure. The density is 2.825 g/cm³. It is transparent. ## Colors and Varieties Marioantofilliite occurs in shades from blue to green. Differences in color may result from slight variations in chemical composition or formation conditions. No varieties of this mineral have been distinguished. ## History and Name The mineral was approved by IMA in 2021 (IMA 2021-067). Its name honors Mario Antofilli (born 1952), an Italian mineral and micromount collector who found the first samples of this mineral. The type locality is the Monte Copello-Reppia mine in Liguria, Italy.

Properties

Streak
light blue
Density
2.825
Fracture
None observed
Transparency
Transparent
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of marioantofilliite is possible almost exclusively using advanced analytical methods, such as Raman spectroscopy or X-ray diffraction (XRD). Visually, it is characterized by blue or green, platy crystals forming rosette-like aggregates. ## Distinguishing from Similar Minerals It can be confused with other secondary copper minerals of similar appearance, such as cyanotrichite, aurichalcite, or other minerals from the hydrotalcite supergroup. Definitive differentiation requires specialized laboratory tests. ## Crystal Forms It forms very small, platy crystals with a hexagonal outline, which combine into rosettes and spherical aggregates.

Geological environment

## Genesis Marioantofilliite is a secondary mineral, forming in the oxidation zones of ore deposits. At the type locality, it was found in voids within ophiolitic rocks (serpentinites) containing sulfide mineralization. ## Mineral Associations At the type locality, it co-occurs with minerals such as chalcopyrite, magnetite, carbotronite, nakauriite, and minerals from the serpentine group. ## Localities The only confirmed occurrence of marioantofilliite in the world is its type locality – the Monte Copello-Reppia mine, located near Ne in Liguria, Italy.

Rarity

Extremely rare

For collectors

## Quality Criteria As a micromineral, the value of a specimen is primarily determined by the quality and size of the crystals, their development, and the aesthetics of the aggregate (e.g., rosette form). Rich association with other rare minerals is also important. Purity and intensity of color also enhance the attractiveness of the sample. ## Popular Localities The only source of specimens is the Monte Copello-Reppia mine in Italy, which makes every specimen from this locality extremely valuable for specialized collectors.

Care and storage

## Cleaning Due to its extreme rarity and fragility, specimens should not be cleaned mechanically or chemically. If absolutely necessary, compressed air (from a safe distance) can be used to remove dust. ## What to Avoid Avoid contact with water, acids, solvents, and any chemicals. The mineral is likely sensitive to changes in temperature and humidity. It should not be heated or exposed to direct sunlight. ## Storage Marioantofilliite specimens, typically in the form of micromounts, should be stored exclusively under stable conditions, in specialized perky boxes, to protect them from mechanical damage, dust, and environmental changes.

External references

Sources

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