Paraniite-(Y)

Chemical formula: (Ca,Y,Dy)<sub>2</sub>Y(W<sup>6+</sup>O<sub>4</sub>)<sub>2</sub>As<sup>5+</sup>O<sub>4</sub>

Paraniite-(Y) is an extremely rare calcium yttrium arsenate-tungstate, forming small, tabular crystals of a yellowish color.

## Characteristics Paraniite-(Y) is a very rare mineral from the arsenate and tungstate group. It occurs as very small, tabular or bladed crystals, reaching sizes up to 0.2 mm. The crystals are transparent to translucent and are characterized by a light yellow to yellowish-brown color and a pale yellow streak. ## Physical Properties This mineral exhibits an adamantine luster. Its Mohs hardness is approximately 4.5, and its density, calculated based on the formula and cell parameters, is 6.33 g/cm³. It shows perfect cleavage in one direction. ## History and Name Paraniite-(Y) was first described in 1998 by D.I. Belakovsky, I.V. Pekov, A.V. Voloshin, and J.A. Percaud. The mineral is named in honor of the Brazilian mineralogist Daniel Paraníba, and the suffix "-(Y)" indicates the dominance of yttrium (Y) among the rare earth elements in its composition.

Properties

Mohs hardness
4.5
Luster
Adamantine
Streak
Pale yellow
Density
6.33
Cleavage
Perfect on {010}
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Monoclinic

Diagnostic features

## Identification Amateur identification of paraniite-(Y) is practically impossible due to its microscopic size and extreme rarity. Identification requires advanced analytical techniques, such as energy-dispersive spectroscopy (EDS/WDS) to confirm its unique chemical composition (presence of Ca, Y, W, and As) and X-ray diffraction (XRD) to determine its crystal structure. ## Distinguishing from Similar Minerals It can be confused with other rare secondary minerals of similar color and habit, such as scheelite or other tungstates and arsenates. Definitive differentiation is only possible through chemical analysis. ## Crystal Forms It forms very small, thin, tabular crystals, often with a hexagonal or rhombic outline, as well as elongated bladed forms. They typically occur as single, isolated crystals on the surface of the host rock.

Geological environment

## Genesis Paraniite-(Y) is a secondary mineral, formed in the oxidation zones of polymetallic deposits. At its type locality (Capillitas mine), it forms in vugs and fissures within rhyolitic rock, within the oxidized zone of a tungsten and arsenic-bearing deposit. ## Mineral Associations This mineral co-occurs with minerals such as quartz, kaolinite, hematite, native bismuth, bismuthinite, wolframite, scheelite, mimetite, beudantite, and anglesite. ## Localities The only confirmed occurrence of paraniite-(Y) in the world is its type locality - the Capillitas mine in the Andalgalá department, Catamarca province, Argentina.

Rarity

Extremely rare

For collectors

## Quality Criteria As a microscopic mineral, the main criterion for collectible value is the quality and richness of the host specimen. The most desirable samples are those with well-formed, sharp crystals, clearly visible under a microscope, set against a contrasting background. The number of crystals on a single specimen also significantly increases its value. ## Popular Localities The only source of specimens is the Capillitas mine in Argentina, which makes every specimen from this locality extremely valuable for specialized collectors of rare minerals and micromounts.

Care and storage

## Cleaning Due to its extreme rarity and small crystal size, mechanical cleaning is not recommended and should only be performed by specialists. If absolutely necessary, compressed air can be used to remove loose dust particles. ## What to Avoid Avoid contact with all chemicals, acids, and bases. The mineral is potentially sensitive to ultrasound and sudden temperature changes. It should not be exposed to direct sunlight. ## Storage Specimens of paraniite-(Y) should be stored under stable conditions, in specialized micromount boxes, protected from dust, moisture, and mechanical damage. Storage in darkness will help preserve its original color.

Sources

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