Kozoite-(La)

Chemical formula: LaCO₃(OH)

Kozoite-(La) is a rare lanthanum hydroxycarbonate, forming microscopic, colorless or white crystals in spherical aggregates.

## Characteristics Kozoite-(La) is a mineral from the carbonate group, chemically classified as lanthanum hydroxycarbonate. It occurs extremely rarely, forming very small, platy or acicular crystals up to 0.1 mm long. These crystals typically arrange themselves into spherical or radial aggregates, which rarely exceed 0.2 mm in diameter. They are colorless to white in appearance, often with a silky or vitreous luster. ## Physical Properties Due to the microscopic size of the crystals, most physical properties are difficult to measure precisely. Hardness and density have not been unambiguously determined. The mineral is transparent to translucent, and its streak is white. ## History and Name The mineral's name honors Dr. Kozō Nagashima (1925-1985), a Japanese chemist from the University of Tsukuba, for his contributions to the analysis of rare earth minerals. The "(La)" suffix in the name indicates the dominant rare earth element in its composition – lanthanum. The mineral was described and approved by the IMA in 2002. ## Uses Kozoite-(La) has no industrial applications. Its significance is purely scientific and collectible, as a rare representative of rare earth carbonates.

Properties

Color
Pink, yellow, white
Luster
Vitreous, Silky
Streak
White
Density
0
Cleavage
Good on {010}
Fracture
Uneven
Transparency
Transparent
Crystal system
Orthorhombic

Diagnostic features

## Identification Identification of kozoite-(La) is possible almost exclusively using advanced analytical methods, such as Raman spectroscopy or X-ray diffraction (XRD) combined with chemical composition analysis (EDS/WDS). Visually, in the field or in a collection, it is practically impossible to distinguish from other microscopic, white secondary minerals without appropriate laboratory equipment. ## Distinguishing from Similar Minerals It can be confused with other minerals from the ankylite group, such as ankylite-(La) or kozoite-(Nd), as well as other microcrystalline carbonates. Certain differentiation requires chemical analysis to determine the dominant rare earth element. ## Crystal Forms It forms elongated, platy crystals that combine into characteristic spherical or hemispherical aggregates with a radial structure.

Geological environment

## Genesis Kozoite-(La) is a secondary mineral, formed as a result of hydrothermal processes or weathering acting on rocks rich in rare earth elements. In its type locality (Matsushiro mine in Japan), it was found in voids within altered volcanic rocks (andesites). ## Mineral Associations It often coexists with other rare earth minerals. In the type locality, it was found in association with laumontite, allanite-(Ce), aegirine, quartz, calcite, fluorite, titanite, ekanite, steacyite, thorogummite, and cerianite-(Ce). ## Localities The most important and best-described occurrence is its type locality: Matsushiro mine, Ehime Prefecture, Japan. It has also been identified in the Pilanesberg alkaline complex in South Africa and in several other pegmatites and carbonatites worldwide, where it occurs in microscopic quantities.

Rarity

Very rare

For collectors

## Quality Criteria As a microscopic mineral, the value of kozoite-(La) is primarily determined by the quality of the specimen on a "micromount" scale. Well-formed, complete spherical aggregates, clearly isolated on the rock matrix, are most prized. The presence of rich associations with other rare minerals is also important. Color and clarity are not of major importance, as the mineral is usually colorless or white. ## Popular Localities The only source of collectible specimens is the Matsushiro mine in Japan, from which the best known examples of this mineral originate.

Care and storage

## Cleaning Specimens should be cleaned only very carefully, using compressed air to remove dust. Due to the extreme fragility and small size of the crystals, any mechanical contact, including with water or a soft brush, risks irreversible damage. ## What to Avoid Avoid contact with all chemicals, especially acids, which will rapidly dissolve it. Avoid ultrasonics, vibrations, and sudden temperature changes. Protect from moisture. ## Storage It is recommended to store specimens exclusively in sealed, lockable "micromount" boxes to protect them from dust, moisture, and mechanical damage. Avoid exposure to direct light, although its sensitivity to UV radiation is unknown.

External references

Sources

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