Leishmanite

Chemical formula: Ba(H₂O)₄[(U₆+O₂)₃O₂(OH)₃]₂·₃H₂O

A very rare, secondary uranium and barium oxide mineral occurring in the oxidation zones of uranium deposits, characterized by strong radioactivity.

## Characteristics Leishmanite is a very rare hydrated uranyl barium oxide. Due to the high uranium content in its complex crystal structure, it is a strongly radioactive mineral. It typically forms fine, microscopic crystals or delicate crusts that are characteristic of secondary uranium minerals formed through weathering. ## Physical properties As a uranyl mineral, leishmanite emits strong ionizing radiation (alpha, beta, and gamma), requiring special precautions during study. Precise physical parameters, such as Mohs hardness or specific gravity, are difficult to determine accurately due to its extreme rarity and the very small size of available crystals. ## Colors and varieties Like the vast majority of other secondary oxide and hydroxide uranium minerals, leishmanite displays bright shades of yellow. This mineral has no known color varieties or trade names. ## History and name The mineral was described based on unique specimens originating from the Grand Alou type locality, located in the Siviez region (Nendaz, Conthey) in the Swiss canton of Valais. ## Uses Due to its extreme natural rarity and microscopic crystal size, leishmanite has absolutely no industrial application as a uranium ore. It is solely an object of deep scientific interest for crystal structure researchers and an extremely rare specimen for highly specialized, systematic mineral collections.

Properties

Crystal system: Orthorhombic

Diagnostic features

## Identification Field identification relies on detecting ionizing radiation using a dosimeter or Geiger-Müller counter and association with other secondary uranium minerals. Definitive confirmation of the mineral species requires advanced analytical studies, such as X-ray diffraction (XRD) and precise chemical analysis. ## Distinguishing from similar minerals Visually, it is practically impossible to distinguish from other yellow secondary uranyl minerals (such as billietite, becquerelite, or compreignacite) without specialized laboratory tests. ## Crystal habits Crystallizes in the orthorhombic system. It forms microscopic crystals and fine aggregates typical of the weathering zones of uranium ores.

Geological environment

## Genesis It is a secondary mineral formed in the oxidation zones of uranium deposits as a result of weathering and alteration of primary uranium minerals in the presence of aqueous solutions rich in barium ions. ## Mineral associations It co-occurs with other secondary uranium minerals characteristic of oxidation and weathering zones. ## Localities The only confirmed locality and type locality for this mineral is Grand Alou (Siviez, Nendaz, Conthey) in the canton of Valais, Switzerland.

Rarity

Extremely rare

For collectors

## Quality criteria For such rare minerals, the value of a specimen is primarily determined by a confirmed origin from the type locality and the presence of well-formed crystals visible under magnification. ## Popular localities The only source of specimens on the collector market is the Swiss type locality Grand Alou in the canton of Valais.

Care and storage

## Cleaning Specimens should not be mechanically cleaned or washed in water to prevent the generation of radioactive dust or solutions. Any handling should be kept to an absolute minimum. ## What to avoid Inhalation of dust and direct contact with skin must be strictly avoided due to strong radioactivity. As a hydrated mineral, leishmanite can be sensitive to humidity changes and elevated temperatures, leading to irreversible dehydration and structure destruction. ## Storage Requires specialized storage in sealed lead containers or appropriately shielded display cabinets. The room must be well ventilated due to the risk of radon accumulation - a radioactive gas that is a natural decay product of uranium.

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External references

https://www.mindat.org/min-499982.html