Mendozavilite-NaCu

Chemical formula: [Na₂(H₂O)₁₅Cu²⁺(H₂O)₆][Mo⁶⁺₈P₂Fe³⁺₃O₃₄(OH)₃]

Mendozavilite-NaCu is a very rare, secondary molybdate with a complex chemical composition, forming microscopic, tabular crystals of an intense green color.

## Characteristics Mendozavilite-NaCu is a complex oxysalt mineral of molybdenum, phosphorus, and iron, belonging to the mendozavilite group. It occurs as very small, thin, tabular crystals with a hexagonal outline, usually not exceeding 0.2 mm. These crystals form rosette-like aggregates, coatings, and crusts on rock surfaces. Due to its microscopic size, it is a mineral primarily accessible to specialized collectors. ## Physical Properties Crystals exhibit a vitreous luster. Hardness and density have not been precisely measured due to the small size and rarity of the material. The mineral is transparent to translucent. ## Colors and Varieties It is characterized by a vivid, emerald-green color. No varieties are known. ## History and Name The mineral was approved by the IMA in 1996. Its name refers to the end member of the series – mendozavilite – with the addition of the suffix "-NaCu" indicating the dominant cations in its structure (sodium and copper). Mendozavilite was named in honor of Eugenio Mendoza (1909-1976), a Mexican mining engineer. ## Uses Due to its extreme rarity and microscopic size, Mendozavilite-NaCu has no industrial application. It is solely an object of scientific and collecting interest.

Properties

Mohs hardness
2.5
Color
Lime green
Luster
Vitreous
Streak
Colorless to very pale green
Density
2.824
Cleavage
{001}
Fracture
Irregular/Uneven
Transparency
Transparent
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of the mineral is based on its characteristic emerald-green color, the form of thin, tabular crystals forming rosette-like aggregates, and its specific occurrence environment. Due to its microscopic size, definitive confirmation requires advanced analytical methods such as Raman spectroscopy or chemical analysis (EDS). ## Distinguishing from Similar Minerals It can be confused with other secondary green copper minerals, such as malachite, brochantite, or atacamite. However, it is distinguished by its unique form of hexagonal, tabular crystals and its co-occurrence with other molybdates in the oxidation zones of molybdenum deposits. ## Crystal Forms It forms thin, tabular crystals with a hexagonal outline, which often combine into rosette-like or fan-shaped aggregates. It also occurs as thin coatings and crusts.

Geological environment

## Genesis It is a secondary mineral, formed in the oxidation zones of hydrothermal molybdenum-copper deposits. It crystallizes under low pH (acidic) conditions from solutions rich in molybdenum, phosphorus, iron, copper, and sodium, originating from the weathering of primary sulfides (mainly molybdenite and chalcopyrite). ## Mineral Associations It co-occurs with other rare secondary minerals such as paramendozavilite, powellite, gypsum, jarosite, as well as molybdenite and pyrite. ## Localities The only known locality for this mineral (type locality) is the Chuquicamata mine in the Antofagasta region, Chile. This is the world's largest open-pit copper mine, known for the occurrence of many rare secondary minerals.

Rarity

Extremely rare

For collectors

## Quality Criteria The most prized specimens are those that possess rich, well-formed, rosette-like aggregates of intensely green crystals, clearly visible against a contrasting matrix. Due to the microscopic nature of the mineral, the quality of the specimen under magnification is crucial. The size of individual crystals and entire aggregates significantly increases value. ## Popular Localities All known collector specimens originate from a single location in the world – the Chuquicamata mine in Chile.

Care and storage

## Cleaning Specimens should be cleaned only very carefully, using compressed air to remove dust. Any contact with water or other liquids is highly inadvisable, as the mineral may be soluble in them. ## What to Avoid Absolutely avoid contact with water, chemicals, ultrasound, and sudden temperature changes. Fragile crystals are very susceptible to mechanical damage. ## Storage Specimens should be stored under stable conditions, in closed, airtight containers (such as "micromount boxes"), away from moisture, dust, and direct sunlight. It is best to store them in a dry place.

External references

Sources

Read more