Liandratite

Chemical formula: U<sup>6+</sup>Nb<sup>5+</sup><sub>2</sub>O<sub>8</sub>

Liandratite is an extremely rare uranium and niobium mineral, forming small, hexagonal, reddish-brown crystals in granitic pegmatites.

## Characteristics Liandratite is a very rare uranium and niobium oxide. It occurs as extremely small, thin, platy crystals with a hexagonal outline, rarely exceeding one millimeter in size. These crystals often form small, radial aggregates and rosettes. Due to its size, it is a typical micromount mineral, requiring magnification for observation. ## Physical Properties Liandratite crystals are brittle. The mineral has a hardness of approximately 3.5 on the Mohs scale and a significant density of 6.35 g/cm³, resulting from the presence of heavy elements - uranium and niobium. The luster is described as resinous to subadamantine. It is a translucent mineral. ## Colors and Varieties Liandratite has a characteristic, intense color ranging from reddish-brown to orange-brown. No color or commercial varieties are distinguished. ## History and Name The mineral was described in 1977 by Fabien Cesbron, M. C. S. Sicha, and R. Giraud. Its name honors the French mineralogist Guy Liandrat (1933-1976), who studied pegmatites in Madagascar. The type locality is the Antandrokomby pegmatite in the Sahatany Valley, Madagascar. ## Uses Due to its extreme rarity and microscopic size, liandratite has no industrial applications. It is solely an object of scientific interest and is valued by specialized collectors of rare minerals.

Properties

Mohs hardness
3.5
Luster
Resinous
Streak
Light brown
Density
6.35
Cleavage
Perfect on {0001}
Transparency
Translucent
Crystal system
Hexagonal

Diagnostic features

## Identification Characteristic features of liandratite include its form - thin, hexagonal plates, intense reddish-brown color, and occurrence in pegmatite vugs. A key diagnostic feature is strong radioactivity, easily detectable with a Geiger counter. Due to its size, identification usually requires stereoscopic magnification. ## Distinguishing from Similar Minerals Liandratite is sometimes confused with other small, brown secondary minerals from pegmatites, such as some minerals from the pyrochlore group. However, its distinctly platy, hexagonal crystal shape distinguishes it. Certain identification most often requires chemical analysis (EDS). ## Crystal Forms It forms thin, hexagonal plates and tablets. These crystals can occur individually or form small, radial aggregates and rosettes on the surface of other minerals.

Geological environment

## Genesis Liandratite is a secondary hydrothermal mineral, crystallizing in the late stage of the evolution of complex granitic pegmatites. It forms in miarolitic cavities as a result of alterations of primary uranium and niobium-bearing minerals, such as uraninite and columbite. ## Mineral Associations It most often co-occurs with minerals typical of pegmatites, such as quartz, feldspars (especially albite), micas, as well as rarer minerals like columbite, uraninite, beta-uranophane, and iochroite (one of its alteration products). ## Localities The most important and well-known occurrence of liandratite, from which the best specimens originate, is its type locality - the pegmatites in the Sahatany Valley, Madagascar. It is a mineral known from only a few localities worldwide.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a liandratite specimen is assessed based on the sharpness and size of the hexagonal crystals, their transparency, and the intensity of their color. Well-formed, undamaged crystals or their rosette aggregates, set on a contrasting matrix, such as white albite or quartz, are most highly valued. ## Popular Localities For collectors, virtually the only source of liandratite specimens is the pegmatites from the Sahatany Valley, Madagascar. Specimens from this locality are considered classic for this species.

Care and storage

## Cleaning Liandratite specimens, as micromount minerals, are extremely delicate. For dust removal, it is best to use compressed air (from a safe distance) or a very soft, dry brush. Wet cleaning and the use of any chemical agents should be avoided. ## What to Avoid Liandratite is a radioactive mineral due to its uranium content and should be handled with caution. Avoid direct, prolonged contact and inhalation of dust. It should not be heated or exposed to strong chemicals. Ultrasonic cleaners can damage delicate crystals. ## Storage It is recommended to store specimens in closed, airtight containers (e.g., "perky boxes") to limit potential radon emission and protect against dusting. Each container must be clearly labeled as radioactive material. It should be kept away from other minerals that may be sensitive to radiation.

Sources

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