Pararaisaite

Chemical formula: Cu<sup>2+</sup>Mg[Te<sup>6+</sup>O<sub>4</sub>(OH)<sub>2</sub>]·6H<sub>2</sub>O

Pararaisaite is a very rare, secondary copper, magnesium, and tellurium mineral, forming blue-green, tabular crystals.

## Characteristics Pararaisaite is a hydrated copper and magnesium tellurate. It occurs as small, bladed or tabular crystals, which typically form rosette-like or radial aggregates and clusters. Individual crystals rarely exceed 0.2 mm in length. Due to its composition and formation conditions, it is a mineral of purely scientific and collectible interest. ## Physical Properties Pararaisaite crystals exhibit a vitreous luster. The hardness of the mineral has not been precisely determined but is estimated to be around 2-3 on the Mohs scale, which is typical for many secondary tellurates. It is a brittle mineral. ## Colors and Varieties Pararaisaite has a characteristic, intense blue-green color. No color varieties or commercial names are distinguished. ## History and Name The mineral's name refers to its close structural and chemical relationship with raisaite. The prefix "para-" indicates a different crystallographic symmetry (monoclinic) compared to the triclinic raisaite. It was recognized as a new mineral by the International Mineralogical Association (IMA) in 2012 under number IMA 2012-027. It was described by Stuart J. Mills and co-workers. ## Uses Pararaisaite has no industrial applications. It is solely of interest to collectors specializing in rare minerals and scientists studying tellurium mineralogy.

Properties

Mohs hardness
2-3
Luster
Vitreous
Streak
Pale blue
Cleavage
Perfect on {001}
Fracture
Brittle
Transparency
Transparent
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of pararaisaite in collecting conditions is based on its characteristic blue-green color, the form of small, tabular crystals forming rosette aggregates, and its co-occurrence with other rare tellurates and tellurides. Definitive identification is only possible using advanced analytical methods such as X-ray diffraction (XRD) and energy-dispersive spectroscopy (EDS). ## Distinguishing from Similar Minerals Pararaisaite is visually very similar to raisaite, from which it differs in crystallographic system. It can also be confused with other secondary, blue-green copper minerals, such as chalcanthite, brochantite, or some tellurates (e.g., teineite). Distinguishing it from these minerals without specialized analysis is practically impossible. ## Crystal Forms It forms thin, tabular or bladed crystals, often with a hexagonal outline, which combine into radial or rosette aggregates. These clusters rarely exceed 1 mm in size.

Geological environment

## Genesis Pararaisaite is a secondary mineral, forming in the oxidation zones (gossans) of ore deposits rich in tellurium. It forms as a result of the weathering of primary tellurides and copper minerals under conditions of low temperature and pressure. ## Mineral Associations This mineral occurs in association with other rare tellurium minerals. In its type locality (Otto Mountain mine), it was found in association with raisaite, adanite, chalcanthite, gypsum, quartz, native gold, native tellurium, and minerals from the allophane group. ## Localities The only confirmed locality for pararaisaite in the world is its type locality: the Otto Mountain mine, located approximately 16 km east of Baker, in San Bernardino County, California, USA.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a pararaisaite specimen is primarily assessed based on the richness and size of the crystal aggregates on the rock matrix. The most desirable specimens are those with clearly formed, undamaged crystal rosettes of intense, blue-green color. Due to the microscopic size of the crystals, the overall aesthetics of the sample and the contrast with associated minerals are also important. ## Popular Localities The only source of pararaisaite specimens is the Otto Mountain mine in California, USA. All samples available on the collector's market originate from this single location.

Care and storage

## Cleaning Due to its extreme rarity and fragility, pararaisaite specimens should not be cleaned mechanically or chemically. Any contaminants are best left undisturbed. If absolutely necessary, compressed air can be used from a safe distance to remove loose dust particles. ## What to Avoid Avoid contact with water, acids, bases, and all solvents. The mineral is likely sensitive to changes in temperature and humidity. It should not be heated or exposed to direct sunlight, which can cause dehydration and color change. ## Storage Pararaisaite specimens should be stored exclusively in specialized, sealed "micromount" containers that protect them from mechanical damage, dust, and humidity changes. Avoid touching the specimens.

Sources

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