Paramendozavilite

Chemical formula: NaAl<sub>4</sub>Fe<sup>3+</sup><sub>7</sub>(PO<sub>4</sub>)<sub>5</sub>(PMo<sup>6+</sup><sub>12</sub>O<sub>40</sub>)(OH)<sub>16</sub>·56H<sub>2</sub>O

Paramendozavilite is a very rare, hydrated iron, sodium, and aluminum phosphate-polymolybdate, forming microscopic, tabular crystals of a yellowish-green color.

## Characteristics Paramendozavilite is a complex, hydrated phosphate-polymolybdate belonging to the mendozavilite group. It occurs as extremely small, tabular crystals with a hexagonal outline, rarely exceeding 0.2 mm. These crystals form rosette-like aggregates, coatings, and thin crusts on rock surfaces. Due to the microscopic size of the crystals, its visual features are difficult to assess without specialized equipment. ## Physical Properties Paramendozavilite crystals exhibit a vitreous luster. They are transparent to translucent. Hardness and density have not been precisely measured due to the small size and fragility of the samples. The mineral is brittle. ## Colors and Varieties Paramendozavilite has a characteristic yellowish-green color. No varieties have been distinguished. ## History and Name The mineral's name refers to its close structural relationship with mendozavilite. The prefix "para-" indicates polymorphism, meaning a different crystal structure with the same chemical composition. It was first described in 1998 based on samples from the Chuquicamata mine in Chile. ## Uses Paramendozavilite has no industrial applications. It is solely an object of scientific and collector interest for specialists accumulating rare minerals and microminerals.

Properties

Mohs hardness
2
Luster
Vitreous
Streak
Pale yellow-green
Density
2.95
Cleavage
Perfect on {010}
Fracture
Micaceous
Transparency
Transparent to Translucent
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of paramendozavilite is possible almost exclusively using advanced analytical methods, such as X-ray diffraction (XRD) and chemical microanalysis (EDS/WDS). Visually, in the field or in a collection, it can only be tentatively suspected based on its yellowish-green color, characteristic microscopic, hexagonal crystals forming rosette-like aggregates, and its association with other rare molybdates in the oxidation zones of copper-molybdenum deposits. ## Distinguishing from Similar Minerals It can be confused with other minerals from the mendozavilite group (like mendozavilite itself) and other secondary molybdates of similar color. Definitive differentiation from mendozavilite requires confirmation of a monoclinic crystal system, in contrast to the triclinic mendozavilite. Other similar minerals, such as schoenite, usually have different crystal morphologies. ## Crystal Forms It forms very small, thin, tabular crystals with a hexagonal outline. These crystals often combine into rosette-like or fan-shaped aggregates, and also form thin coatings and crusts.

Geological environment

## Genesis Paramendozavilite is a secondary mineral, forming under extremely dry climatic conditions. It forms in the oxidation zones (gossans) of porphyry copper and molybdenum deposits. Its formation is a result of the weathering of primary sulfides, mainly molybdenite. ## Mineral Associations It most commonly co-occurs with other rare, secondary molybdates and sulfates. Typical associated minerals include mendozavilite, schoenite, lindgrenite, brochantite, antlerite, gypsum, as well as quartz and hematite. ## Localities The most important and best-documented occurrence, which is also the type locality, is the Chuquicamata mine in the Antofagasta region of Chile. This is the world's largest open-pit copper mine, known for the occurrence of many rare secondary minerals. Other reports of its occurrence, e.g., from a mine in Utah (USA), require further verification.

Rarity

Very rare

For collectors

## Quality Criteria The collector appeal of a specimen depends on the richness and development of its microscopic crystals. Samples with clearly formed, rosette-like aggregates of intense yellowish-green color, contrasting with the rock matrix, are most valued. Due to its microscopic nature, the quality of a specimen is assessed under high magnification. ## Popular Localities The only confirmed and recognized source of collector specimens is the Chuquicamata mine in Chile. Samples from this locality are the standard for this mineral.

Care and storage

## Cleaning Specimens should be handled with utmost care. Cleaning is not recommended due to the extreme delicacy and reactivity of the mineral. Dust can only be removed with a gentle stream of compressed air from a safe distance. ## What to Avoid Contact with water, which can dissolve or damage the crystals, must be strictly avoided. The use of any chemical agents, ultrasonics, and exposure to changes in temperature and humidity are also inadvisable. The mineral is unstable under conditions other than those prevailing in the dry climate of its occurrence. ## Storage Paramendozavilite specimens must be stored in sealed, dry containers, preferably with a desiccant (e.g., silica gel). The safest form of display is a specialized "micromount" box, protecting against mechanical damage and external factors.

Sources

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