Lagalyite

Chemical formula: Ca<sub>2x</sub>Mn<sup>4+</sup><sub>1-x</sub>O<sub>2</sub>·1.5-2H<sub>2</sub>O (x = 0.05-0.08)

Lagalyite is a very rare, hydrated manganese oxide, forming microscopic, hexagonal plates with a metallic luster.

## Characteristics Lagalyite is a hydrated manganese oxide with a complex chemical composition. It occurs as extremely small, hexagonal, platy crystals, typically not exceeding 10 micrometers in diameter and 1 micrometer in thickness. These crystals form aggregates and coatings. Due to the microscopic size of the crystals, its visual characteristics are difficult to assess with the naked eye. ## Physical Properties Lagalyite crystals exhibit a metallic luster. The mineral is opaque. Its hardness and density have not been precisely determined due to its microscopic size and rarity, however, the calculated density based on its formula is approximately 3.05 g/cm³. ## Colors and Varieties Lagalyite is black in color, and in reflected light, it is grayish-white. No color or commercial varieties are known. ## History and Name The mineral was first described in 1999 by J. Post, P. Heaney, R. von Dreele, C. Kort, and V. Diomidis. Its name honors Professor Gerhard Lagaly (1938-2021) from Kiel University (Germany), in recognition of his contributions to the chemistry of layered minerals and manganese oxides. ## Applications Lagalyite has no industrial applications. It is solely an object of scientific and collecting interest for specialists who collect microscopic minerals.

Properties

Luster
Metallic
Streak
Black
Density
3.05
Cleavage
Perfect on {0001}
Transparency
Opaque
Crystal system
Hexagonal

Diagnostic features

## Identification Identification of lagalyite is only possible using advanced laboratory methods, such as X-ray diffraction (XRD) and scanning electron microscopy with chemical composition analysis (SEM-EDS). Under collecting conditions, it is unrecognizable without a label from a confirmed locality. ## Distinguishing from Similar Minerals It can be confused with other black manganese oxides, such as birnessite, todorokite, or pyrolusite, from which it can only be distinguished by specialized analysis of its crystal structure and chemical composition. ## Crystal Forms It forms microscopic, hexagonal, thin plates that aggregate into rosetted or spherulitic clusters, and also form thin coatings and efflorescences on other minerals.

Geological environment

## Genesis Lagalyite is a secondary mineral, forming in the oxidation zones of manganese deposits. It forms under low-temperature conditions as a result of weathering and transformation of other primary manganese minerals. ## Mineral Associations It co-occurs with other manganese minerals, such as birnessite, todorokite, cryptomelane, as well as with calcite and quartz. ## Localities The only confirmed occurrence (type locality) is the South-Artinsk mine in the Sverdlovsk Oblast, Ural Mountains, Russia.

Rarity

Extremely rare

For collectors

## Quality Criteria As a microscopic mineral, lagalyite is not evaluated according to typical criteria. The value of a specimen depends on the confirmation of its identity through scientific analysis and on the abundance and quality of microscopic crystals visible under high magnification. The most valuable samples are those with well-formed, rosetted aggregates on a contrasting background. ## Popular Localities The only source of specimens is the type locality – the South-Artinsk mine in Russia.

Care and storage

## Cleaning Specimens containing lagalyite should not be cleaned mechanically or chemically. Dust can only be removed using a photographic air blower or compressed air from a safe distance. ## What to Avoid Avoid contact with water, acids, detergents, and any liquids. The mineral is potentially sensitive to changes in humidity and temperature, which can lead to its dehydration and disintegration. Protect it from ultrasound and vibrations. ## Storage Store in stable conditions, in a closed, transparent "micromount" box, protecting it from dust, moisture, and mechanical damage. It does not require special protection from light.

Sources

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