Agricolaite

Chemical formula: K<sub>4</sub>(U<sup>6+</sup>O<sub>2</sub>)(CO<sub>3</sub>)<sub>3</sub>

Agricolaite is a rare, secondary uranium mineral, forming thin, flexible lamellae with a pearly luster and strong fluorescence under UV light.

## Characteristics Agricolaite is a hydrated potassium uranyl carbonate. It occurs as coatings, efflorescences, and aggregates of small, flexible lamellae or scales that can bend without breaking. Individual crystals are very small, tabular, and rarely visible to the naked eye. This mineral is characterized by a distinct pearly luster on cleavage surfaces, giving it a shiny appearance. ## Physical Properties Agricolaite lamellae are transparent to translucent. Its density is calculated to be 3.23 g/cm³. One of its most characteristic physical features is strong, greenish-yellow fluorescence under ultraviolet light (both shortwave and longwave). As a uranium mineral, it is radioactive. ## Colors and Varieties Agricolaite is most often colorless, white, pale yellow, or pale green. No named color varieties are distinguished. ## History and Name The mineral was first described in 2011 by a team of mineralogists led by Jakub Plášil. Its name honors Georgius Agricola (1494–1555), a German scholar and physician, considered the "father of mineralogy" for his pioneering work "De re metallica". The type locality (locus typicus) is Jáchymov in the Czech Republic. ## Uses Due to its rarity and small occurrences, agricolaite has no industrial application. However, it is a valued and sought-after collector's mineral.

Properties

Luster
Pearly
Streak
White
Density
3.23
Cleavage
Perfect on {001}
Transparency
Transparent to Translucent
Crystal system
Monoclinic

Diagnostic features

## Identification The most important diagnostic feature of agricolaite is its very strong, greenish-yellow fluorescence under UV light. Its characteristic form of occurrence as aggregates of thin, flexible lamellae with a pearly luster is also distinctive. Radioactivity measurement with a Geiger counter is also helpful in identification. ## Distinguishing from Similar Minerals Agricolaite can be confused with other secondary uranium minerals of similar appearance and fluorescence, such as schröckingerite, andersonite, or liebigite. Distinguishing them often requires advanced analytical methods (XRD, EDS). From visually similar, non-fluorescent platy minerals (e.g., some micas), it is distinguished by strong fluorescence and radioactivity. ## Crystal Forms It forms aggregates composed of microscopic, tabular crystals. Macroscopically, it occurs as thin coatings, efflorescences, and also aggregates of small, flexible scales.

Geological environment

## Genesis Agricolaite is a secondary mineral, forming in the oxidation zones of uranium deposits, often in post-mining environments (on the walls of old mine workings). It forms by precipitation from solutions rich in uranium and carbonates, under low temperature and pressure conditions. ## Mineral Associations It most often co-occurs with other secondary uranium minerals, such as schröckingerite, andersonite, liebigite, and also with gypsum. The primary source of uranium is usually uraninite. ## Localities The most important and best-known locality, which is also the type locality, is Jáchymov in the Czech Republic. It is also known from several other localities in Germany (e.g., in the Ore Mountains).

Rarity

Very rare

For collectors

## Quality Criteria The collector's value of a specimen is primarily determined by the abundance and surface area covered by the mineral, as well as the intensity of its color and fluorescence. Specimens where agricolaite forms rich, thick coatings are particularly prized. Co-occurrence with other rare, well-formed uranium minerals also increases its attractiveness. ## Popular Localities The vast majority of the best collector specimens come from the historic uranium mine in Jáchymov, Czech Republic.

Care and storage

## Cleaning Agricolaite specimens are very delicate and sensitive to moisture. They should only be dry-cleaned using a soft brush or a stream of compressed air to remove dust. Absolutely avoid contact with water and other liquids. ## What to Avoid The mineral is sensitive to changes in humidity and can be damaged by contact with water. All chemicals, ultrasonics, and sudden temperature changes should be avoided. As a uranium mineral, it is radioactive – avoid inhaling dust and wash hands after each contact with a specimen. ## Storage It is recommended to store specimens in a dry, sealed container (e.g., a "membrane box" or a sealed box) to protect them from moisture and mechanical damage. Due to radioactivity, specimens should be kept away from areas of constant human presence, and the container should be appropriately labeled.

Sources

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