Lermontovite

Chemical formula: U⁴⁺PO₄(OH)·H₂O

Lermontovite is a rare, secondary uranium mineral characterized by its green color and fibrous appearance, occurring in the oxidation zones of uranium deposits.

## Characteristics Lermontovite is a hydrated uranyl phosphate that forms felt-like aggregates or earthy masses. Its structure consists of tiny, acicular or fibrous crystals, which are rarely visible to the naked eye. It typically occurs as crusts and coatings on other uranium minerals. Due to its chemical composition, this mineral is strongly radioactive. ## Physical Properties Lermontovite crystals are very fine and delicate. This mineral is characterized by a silky luster in the case of fibrous aggregates or a dull luster in the case of earthy masses. It is opaque. Its hardness and density are difficult to measure precisely due to the nature of its aggregates, but they are estimated to be approximately 2 on the Mohs scale and 3.86 g/cm³ (calculated value), respectively. ## Colors and Varieties Lermontovite most commonly exhibits colors ranging from yellowish-green to olive-green. No distinct color varieties or commercial varieties are recognized. ## History and Name The mineral was first described in 1914 by the Russian mineralogist Konstantin A. Nenadkevich. The name comes from Mikhail Lermontov (1814–1841), a famous Russian poet and writer, in recognition of his contribution to Russian culture. The originally described material was likely a mixture, and the mineral was discredited. It was re-approved as a distinct mineral species in 1957 based on new research. ## Uses Lermontovite, like other secondary uranium minerals, has no direct industrial application. Its significance is limited to the scientific sphere as an indicator of geochemical processes in uranium deposits and to the interest of specialists collecting radioactive minerals.

Properties

Mohs hardness
2
Color
Grayish green, green
Luster
Silky
Streak
Greenish yellow
Density
4.00
Cleavage
Perfect on {010}
Fracture
Uneven
Transparency
Transparent
Crystal system
Orthorhombic

Diagnostic features

## Identification Lermontovite can be identified by its characteristic, felt-like or earthy aggregates of a greenish color. A key diagnostic feature is its occurrence in the oxidation zones of uranium deposits and its very strong radioactivity, easily detectable with a Geiger counter. ## Distinguishing from Similar Minerals It can be confused with other secondary uranium minerals of similar appearance, such as autunite or torbernite, which, however, often form better-developed, platy crystals and exhibit fluorescence under UV light, which lermontovite does not possess. From other green, earthy minerals, it is primarily distinguished by its extreme radioactivity. ## Crystal Forms It forms microscopic, acicular or bladed crystals that combine into dense, matted aggregates resembling felt. It also occurs as earthy, powdery aggregates and as crusts.

Geological environment

## Genesis Lermontovite is a secondary mineral, forming in the oxidation (weathering) zones of hydrothermal uranium deposits. It forms as a result of the alteration of primary uranium minerals, such as uraninite, under low temperature and pressure conditions, in the presence of phosphate-rich waters. ## Mineral Associations It often co-occurs with other secondary uranium minerals, such as ningyoite, phosphuranylite, saleeite, torbernite, autunite, as well as with gypsum, kaolinite, and quartz. ## Localities The most important and classic localities for this mineral are in Russia, in the Caucasus Mountains (Pyatigorsk region, Mount Beshtau), from where the first described specimens originated. It has also been reported in Germany (Saxony), the Czech Republic (Příbram), and the United States (Utah).

Rarity

Very rare

For collectors

## Quality Criteria The collector's appeal of lermontovite primarily depends on the richness and purity of the aggregates. The most prized specimens are those with visible, dense, felt-like aggregates of an intense green color, covering a significant area of the matrix rock. A well-documented locality is also important, especially if it is one of the classic sites. ## Popular Localities The historical localities in the Pyatigorsk region of Russia are considered the best for this mineral. Specimens from these locations are rare on the collector's market and command high prices. This mineral is sought after mainly by specialized collectors of rare and radioactive minerals.

Care and storage

## Cleaning The mineral is extremely delicate and sensitive to water. Mechanical cleaning is not recommended. If necessary, a stream of compressed air can be used to remove dust. Contact with water should be avoided, as it can damage and alter the mineral's structure. ## What to Avoid Lermontovite is an unstable mineral. Contact with water, acids, and other chemicals must be strictly avoided. It should be protected from moisture, high temperatures, and direct sunlight, which can lead to its dehydration and decomposition. Due to its strong radioactivity, exposure should be limited, and hands should always be washed after contact with a specimen. ## Storage Lermontovite specimens must be stored in dry conditions, preferably in tightly sealed containers (e.g., "perky boxes") away from other minerals that could be damaged by radiation. Due to radioactivity, it should be stored in a place inaccessible to children and pets, with appropriate labeling.

External references

Sources

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