Lanthanite-(La)

Chemical formula: La₂(CO₃)₃(H₂O)₆·₂H₂O

Lanthanite-(La) is a rare, hydrated lanthanum carbonate, forming small, platy crystals with a pearly luster, prized by collectors of rare minerals.

## Characteristics Lanthanite-(La) is a hydrated lanthanum carbonate belonging to the lanthanite group. This mineral typically forms very small, thin, platy crystals, often aggregated into rosette-like or radial clusters, as well as earthy and powdery masses. The crystals are usually too small to be observed with the naked eye. Due to its softness and fragility, it is primarily a mineral of scientific and collector interest. ## Physical Properties Lanthanite-(La) is a very soft mineral with a Mohs hardness of only 2.5, meaning it can be scratched with a fingernail. It exhibits perfect cleavage in one direction, contributing to its platy appearance. The luster is typically pearly on cleavage surfaces or dull in the case of earthy masses. It is a relatively light mineral, with a density of approximately 2.74 g/cm³. ## Colors and Varieties This mineral is most commonly colorless, white, grayish-white, or pale pink. Pink coloration is often associated with neodymium admixture. No named varieties of this mineral are distinguished. ## History and Name The name "lanthanite" comes from the dominant element in its composition – lanthanum. The suffix "-(La)" was added according to the naming rules for minerals of the lanthanite group to indicate that lanthanum is the dominant rare-earth element in this specific mineral. It was first described in 1845 based on material collected in Bastnäs, Västmanland region, Sweden. ## Uses Lanthanite-(La) has no industrial applications due to its rarity and small crystal size. It is solely an object of interest for collectors specializing in rare-earth minerals and scientists.

Properties

Mohs hardness: 2.5-3
Color: White, colourless, yellowish, pinkish
Luster: Pearly
Streak: White
Density: 0
Cleavage: {010}
Fracture: Irregular/Uneven
Transparency: Translucent
Crystal system: Orthorhombic

Diagnostic features

## Identification Identifying lanthanite-(La) in the field is practically impossible without specialized equipment. In a collection, it is identified based on characteristic, small, platy crystals with a pearly luster, often in the form of rosettes. Key features include extreme softness (hardness 2.5) and perfect cleavage. It reacts with acids, releasing carbon dioxide bubbles. Final confirmation requires advanced analyses, such as X-ray diffraction (XRD) or EDS spectroscopy to determine chemical composition. ## Distinguishing from Similar Minerals Lanthanite-(La) can be confused with other minerals from the lanthanite group, such as lanthanite-(Ce) and lanthanite-(Nd). Differentiation between them is only possible through chemical analysis determining the dominant rare-earth element. It may also resemble other secondary carbonates or sulfates with light color and pearly luster, but its very low hardness and specific crystal forms are helpful in distinguishing it. ## Crystal Forms Crystals are thin, platy, with rhombic or pseudohexagonal outlines. They usually occur as small, radial or rosette-like aggregates, as well as coatings and efflorescences or in earthy masses.

Geological environment

## Genesis Lanthanite-(La) is a secondary mineral, forming in the weathering (oxidation) zones of ore deposits and pegmatites rich in rare-earth elements. It forms as a result of the alteration and decomposition of primary lanthanum-bearing minerals, such as allanite, cerite, bastnäsite, or monazite, under the influence of carbon dioxide-containing waters. ## Mineral Associations It often co-occurs with the minerals from which it forms, such as allanite, bastnäsite, cerite, as well as other secondary rare-earth minerals like lanthanite-(Ce), lanthanite-(Nd), calcite, fluorite, and various iron oxides. ## Localities The most important localities yielding well-formed specimens include the Bastnäs mine in Sweden (type locality), Saucon Valley in Pennsylvania (USA), as well as some locations in Norway and Russia. It occurs in many places worldwide, but rarely in the form of well-developed crystals suitable for collecting.

Rarity

Rare

For collectors

## Quality Criteria The most prized specimens by collectors are those with sharp, well-formed, though usually microscopic, crystals forming aesthetic rosettes or radial aggregates. A distinct pearly luster and pure color (white or pale pink) are desirable. Crystal size is a key factor – specimens with crystals visible to the naked eye are exceptionally rare and valuable. It is also important that the delicate crystals are intact and embedded on a contrasting rock matrix. ## Popular Localities Classic and most well-known specimens come from the Bastnäs mine in Sweden. Good quality microcrystals have also been found in Bethlehem, Pennsylvania, USA.

Care and storage

## Cleaning Lanthanite-(La) specimens are extremely delicate and sensitive. Mechanical cleaning is highly inadvisable. If absolutely necessary, a very gentle stream of compressed air can be used to remove loose dust. Avoid contact with water, which can damage the mineral. ## What to Avoid Absolutely avoid contact with water, acids, and other chemicals. The mineral is very soft, susceptible to scratches and mechanical damage. It should not be heated or exposed to temperature changes. Store away from moisture. ## Storage It is recommended to store specimens in sealed, padded "micromount" boxes to protect them from physical damage, dust, and moisture. Display should be in enclosed display cases, away from direct light and sources of vibration.