Biraite-(La)

Chemical formula: La₂Fe₂+(CO₃)(Si₂O₇)

A very rare lanthanum and iron silicate-carbonate, forming microscopic, brown crystals in skarns.

## Characteristics Biraite-(La) is a complex silicate-carbonate belonging to the group of rare minerals. It occurs as very small, prismatic or acicular crystals, rarely exceeding 0.2 mm in length. These crystals often form radial or chaotic aggregates. It is typically brown, yellowish-brown to reddish-brown. Due to the microscopic size of the crystals, its features are most often observed under magnification. ## Physical Properties This mineral is characterized by a hardness of approximately 5 on the Mohs scale. It has a vitreous luster and is translucent. Its density, calculated based on chemical composition and structure, is approximately 4.66 g/cm³, which is a high value, typical for minerals containing rare earth elements. ## Colors and Varieties Observed colors of biraite-(La) include shades from yellowish-brown through brown to reddish-brown. No color varieties or commercial varieties are known. ## History and Name The name "Biraite" comes from the Bira River, near which its type locality in Russia is situated. The suffix "-(La)" in the name (according to Levinson's classification) indicates that lanthanum is the dominant rare earth element in this mineral. It was officially recognized by the International Mineralogical Association (IMA) in 2001. ## Uses Biraite-(La) has no industrial applications. It is of interest only for scientific and collecting purposes as a very rare mineral.

Properties

Mohs hardness: 5
Luster: Vitreous
Streak: Pale yellow
Density: 4.66
Cleavage: Good on {100}
Fracture: Uneven
Transparency: Translucent
Crystal system: Monoclinic

Diagnostic features

## Identification Identification of biraite-(La) based on visual features is impossible due to its microscopic size and similarity to many other minerals. Definitive identification requires advanced laboratory techniques, such as X-ray microanalysis (EDS/WDS) to determine chemical composition (confirmation of La, Fe, Si, and the carbonate group is necessary) and X-ray diffraction (XRD) for crystal structure analysis. ## Distinguishing from similar minerals It can be confused with other brown, fine-grained minerals found in skarns, such as some garnets, vesuvianite, or titanite. Differentiation from other rare earth minerals that may co-occur with it is only possible through chemical analysis. ## Crystal forms It forms elongated, prismatic or acicular crystals, often grouped into radial aggregates or chaotic clusters. Crystals are usually very small, reaching at most fractions of a millimeter.

Geological environment

## Genesis Biraite-(La) is a mineral of metasomatic origin. It forms in magnesian-forsterite skarns, which developed at the contact of granitoid intrusions with carbonate rocks. ## Mineral associations This mineral occurs in association with other minerals typical of the skarn environment. These most commonly include forsterite, magnetite, andradite, hedenbergite, clinochlore, vesuvianite, and apatite. ## Localities The only confirmed locality of biraite-(La) in the world is its type locality – the Bira deposit in the Maly Khingan mountain range, in the Jewish Autonomous Oblast in Russia.

Rarity

Extremely rare

For collectors

## Quality criteria As a microscopic mineral, biraite-(La) is primarily valued by specialized micromount collectors. The value of a specimen is determined by the abundance of the mineral on the matrix, the sharpness and development of the crystals (even the smallest ones), and the aesthetic composition with associated minerals. Specimens with well-isolated, radial aggregates on a contrasting background are most desirable. ## Popular localities The only source of specimens is the type locality in Russia. This is not a popular or easily accessible locality; specimens come from scientific research and rarely enter the collector's market.

Care and storage

## Cleaning Specimens of biraite-(La) are typically micromounts, which are very delicate. Cleaning is not recommended. If necessary, only compressed air (from a safe distance) can be used to remove dust. Avoid contact with water and any chemical agents. ## What to avoid The mineral is sensitive to shocks and mechanical damage. Avoid contact with acids, which can damage it due to the presence of the carbonate group. Store away from moisture and extreme temperatures. ## Storage The safest storage method is a closed micromount box, which protects the specimen from dust, mechanical damage, and sudden environmental changes. Avoid exposure to direct sunlight.

Sources

IMA Mineral List (CNMNC)