Gasparite-(La)

Chemical formula: La₃+(As₅+O₄)

Gasparite-(La) is a rare lanthanum arsenate, forming reddish-brown crusts and small crystals in hydrothermal deposits.

## Characteristics Gasparite-(La) is a lanthanum arsenate belonging to the monazite group. It most commonly occurs as earthy or powdery aggregates, as well as crusts covering other minerals. It rarely forms small, imperfectly developed crystals with a tabular or equant habit. Its appearance is usually inconspicuous, and macroscopic specimens are rare. ## Physical Properties This mineral has a hardness of approximately 5 on the Mohs scale. It exhibits a resinous to subadamantine luster, and can be dull in earthy aggregates. It is translucent to opaque. Its density is significant, at 5.63 g/cm³, which is typical for minerals containing rare earth elements. ## Colors and Varieties It ranges in color from reddish-brown and pinkish to yellowish-brown. No distinct color varieties or commercial varieties are recognized. ## History and Name The mineral's name, approved in 1987, comes from Gaspare "Gaspar" Bonanno, a Sicilian mineral collector and dealer who provided the first samples for study. The suffix -(La) indicates the dominance of lanthanum in its chemical composition, distinguishing it from other minerals in this series. ## Uses Due to its rarity and occurrence in small quantities, gasparite-(La) has no industrial applications. It is solely an object of scientific and collecting interest.

Properties

Mohs hardness: 5
Luster: Resinous
Streak: Light brown
Density: 5.63
Cleavage: Good on {010}
Fracture: Conchoidal
Transparency: Translucent
Crystal system: Monoclinic

Diagnostic features

## Identification Helpful features for identifying gasparite-(La) include its characteristic reddish-brown color, resinous luster, high density, and specific geological environment. A hardness of approximately 5 on the Mohs scale is also an important clue. It often occurs as crusts, which makes identification difficult without specialized equipment. ## Distinguishing from Similar Minerals It can be confused with other rare earth arsenates, such as chernovite-(Y) or agardite, as well as other secondary minerals of similar color, e.g., goethite. It is distinguished from goethite by a lighter streak and higher hardness. Definitive differentiation from other REE arsenates is usually only possible using analytical methods, such as EDS spectroscopy. ## Crystal Forms It most commonly forms crusts, coatings, and earthy and powdery aggregates. Very rarely, small, tabular or pseudo-octahedral crystals are found, usually with imperfect faces.

Geological environment

## Genesis Gasparite-(La) is a secondary mineral, formed in the oxidation zones of hydrothermal deposits and in altered rocks rich in rare earth elements. It forms as a result of the alteration of primary REE minerals (such as allanite or monazite) in an arsenic-rich environment. ## Mineral Associations It co-occurs with other arsenate minerals and those containing rare earth elements. Its most common associations include chernovite-(Y), wakefieldite-(Ce), agardite, allanite-(Ce), hematite, and quartz. ## Localities The most important occurrences of this mineral worldwide are Bivongi in Calabria (Italy), where it was discovered. It is also known from several locations in the canton of Graubünden (Switzerland), as well as from the Clara mine in the Black Forest (Germany), famous for its rare mineral occurrences.

Rarity

Rare

For collectors

## Quality Criteria The most prized by collectors are specimens with visible, even if small, well-formed crystals. Intense, reddish-brown color and placement on a contrasting matrix are highly valued. Co-occurrence with other rare minerals adds significant value, creating attractive association specimens. ## Popular Localities Specimens from the Clara mine in Germany and from localities in the Swiss Alps are, along with material from the type locality in Italy, the most sought after by collectors specializing in rare minerals.

Care and storage

## Cleaning Gasparite-(La) specimens should be cleaned very carefully, preferably dry with a soft brush to remove dust. If necessary, brief washing in distilled water is permissible, but prolonged soaking should be avoided. After wet cleaning, the specimen must be thoroughly dried immediately. ## What to Avoid The mineral contains arsenic, so inhalation of dust should be avoided, and hands should be washed after each contact. It should be protected from contact with acids and other chemicals. It should not be exposed to ultrasound or high temperatures. ## Storage It is recommended to store specimens in closed, padded boxes or display cases to protect them from mechanical damage and dust. Due to its arsenic content, it should be stored in a labeled container, away from children and pets.

Sources

IMA Mineral List (CNMNC)