Percleveite-(La)

Chemical formula: La₂Si₂O₇

Perkleveite-(La) is a very rare lanthanide silicate, forming small, prismatic crystals with a vitreous luster.

## Characteristics Perkleveite-(La) is a mineral belonging to the gadolinite group and datolite subgroup. It occurs as very small, prismatic crystals, reaching sizes up to 0.2 x 0.05 x 0.05 mm, often forming radial aggregates. It is transparent to translucent, with a vitreous luster. ## Physical Properties The mineral has a hardness of approximately 6 on the Mohs scale. Its calculated density is 5.34 g/cm³. It exhibits no cleavage, and its fracture is conchoidal. It is brittle. ## Colors and Varieties Perkleveite-(La) is colorless to pale yellow. It has no known varieties. ## History and Name The name "perkleveite" was given in honor of Per Teodor Cleve (1840-1905), a Swedish chemist and mineralogist who discovered the elements holmium and thulium. The suffix "-(La)" indicates the dominance of lanthanum in its chemical composition. The mineral was approved by the IMA in 2002. ## Uses Due to its extreme rarity and microscopic size, perkleveite-(La) has no applications beyond scientific research. It is of interest solely to specialized collectors of rare minerals.

Properties

Mohs hardness
6
Color
Very pale yellow to colourless in thin fragments to light yellow in aggregates
Luster
Vitreous
Streak
White
Density
5.094
Cleavage
Imperfect {001}
Fracture
Irregular/Uneven
Transparency
Transparent
Crystal system
Tetragonal

Diagnostic features

## Identification Identification of perkleveite-(La) is impossible without advanced analytical techniques such as energy-dispersive spectroscopy (EDS/WDS) or X-ray diffraction (XRD), due to its microscopic size and similarity to other rare-earth silicates. The key is to confirm the dominance of lanthanum in its composition. ## Distinguishing from Similar Minerals It can be confused with other minerals from the gadolinite group, such as gadolinite-(Y), gadolinite-(Ce), or hingganite-(Y). Differentiation requires precise chemical analysis to determine the dominant rare-earth element. ## Crystal Forms It forms elongated, prismatic crystals with a nearly square cross-section. Crystals often occur as radial or randomly oriented aggregates.

Geological environment

## Genesis Perkleveite-(La) forms in the late stages of crystallization in granitic pegmatites, within miarolitic cavities. It is a product of low-temperature hydrothermal processes. ## Mineral Associations This mineral co-occurs with quartz, microcline, albite, fluorite, xenotime-(Y), fergusonite-(Y), and other minerals from the gadolinite group. ## Localities The only confirmed occurrence (type locality) of perkleveite-(La) is the Nya (Sten) granite quarry near the village of Ula (Ulå), in the municipality of Larvik, Vestfold region, Norway.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a perkleveite-(La) specimen is primarily assessed based on its identifiability and the richness of associated minerals. The most desirable specimens are those with well-formed, albeit microscopic, crystals in radial aggregates, set on a contrasting matrix (e.g., quartz or feldspar). Due to their size, the quality of microscopic photography is crucial. ## Popular Localities The only source of specimens is the type locality in Norway, which makes them extremely rare and sought after by collectors specializing in "micromount" minerals and rare-earth element minerals.

Care and storage

## Cleaning Due to the extreme brittleness and small size of the crystals, mechanical cleaning is not recommended. If absolutely necessary, compressed air can be used to remove loose dust particles. Avoid contact with water and chemicals. ## What to Avoid Avoid all acids and chemicals, ultrasonic cleaning, and sudden temperature changes. The mineral is very brittle, so it should be protected from impacts and vibrations. ## Storage Specimens should be stored in stable conditions, in specialized "micromount" boxes, protecting them from dust, moisture, and mechanical damage. Do not expose them to direct sunlight.

External references

Sources

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