Línekite

Chemical formula: K<sub>2</sub>Ca<sub>3</sub>[(U<sup>6+</sup>O<sub>2</sub>)(CO<sub>3</sub>)<sub>3</sub>]<sub>2</sub>·8H<sub>2</sub>O

Línekite is an extremely rare, water-soluble uranyl mineral, distinguished by its intense yellow-green fluorescence under UV light.

## Characteristics Línekite is a hydrated uranyl, potassium, and calcium carbonate. It forms aggregates of prismatic to acicular crystals, which rarely exceed 1 mm in length. Most often, it occurs as thin coatings, efflorescences, and crusts on host rocks, especially on the walls of old mine workings. It is a secondary mineral, formed as a result of the weathering processes of uranium ores. Due to its fragility and solubility, specimens are extremely delicate. ## Physical Properties Línekite crystals exhibit a vitreous luster. The mineral is soft and brittle. Its most characteristic feature is strong, bright yellow-green fluorescence under shortwave and longwave ultraviolet light. It is radioactive due to the presence of uranium. ## Colors and Varieties Línekite ranges in color from pale yellow to yellow-green. No color varieties or commercial varieties are distinguished. ## History and Name The mineral was discovered in Jáchymov, Czech Republic, and described in 2016. It was named in honor of the Czech chemist and mineralogist, Dr. Aleš Línek (1960-2014), in recognition of his contribution to the study of secondary uranium minerals. The type locality is the Svornost mine in Jáchymov. ## Uses Línekite has no industrial applications. It is of scientific and collector's interest only as a very rare secondary uranium mineral.

Properties

Mohs hardness
2-3
Luster
Vitreous
Streak
Pale yellow
Density
2.65
Cleavage
Perfect on {010}
Fracture
Uneven
Transparency
Transparent
Crystal system
Triclinic

Diagnostic features

## Identification The key diagnostic feature of línekite is its intense yellow-green fluorescence under UV light. Water solubility is also a characteristic feature, although destructive to the sample. It occurs as small, acicular crystals forming coatings on rocks. ## Distinguishing from Similar Minerals Línekite can be confused with other secondary uranium minerals of similar color and form, such as andersonite, liebigite, schröckingerite, or bayleyite. It is distinguished from them mainly by detailed chemical (EDS/WDS) and crystallographic (XRD) analyses. Andersonite crystallizes in the trigonal system, and schröckingerite and bayleyite in the monoclinic system, while línekite is triclinic. Liebigite is also triclinic but has a different chemical composition (lack of potassium). ## Crystal Forms It forms prismatic to acicular crystals, often flattened, gathered in radial or chaotic aggregates. It also occurs as thin coatings and efflorescences.

Geological environment

## Genesis Línekite is a secondary mineral, formed in the oxidation zones of uranium deposits. It forms under low-temperature conditions as a result of carbonate-rich waters acting on primary uranium minerals. It is a post-mining mineral, crystallizing on the walls of old, damp mine workings. ## Mineral Associations It most often co-occurs with other secondary uranium minerals, such as schröckingerite, andersonite, liebigite, bayleyite, as well as with gypsum, uraninite, and other ore minerals. ## Localities The only confirmed and described occurrence of línekite in the world is its type locality – the historic Svornost mine in Jáchymov, in the Karlovy Vary region of the Czech Republic.

Rarity

Extremely rare

For collectors

## Quality Criteria The collector's appeal of a línekite specimen depends on the richness and visibility of the crystals on the rock matrix. The most prized specimens are those with well-formed, abundant aggregates of acicular crystals that cover a significant area of the rock. Due to the microscopic size of the crystals, their abundance and color intensity are crucial. Contrast with a dark host rock also enhances visual value. ## Popular Localities The only source of línekite specimens is the Svornost mine in Jáchymov (Czech Republic). Material from this locality is extremely rare and sought after by specialized collectors of uranium minerals.

Care and storage

## Cleaning The mineral must absolutely not be cleaned wet, as it is water-soluble. Dust can only be removed very carefully with a soft brush or a stream of dry air (e.g., from a photographic blower). ## What to Avoid Avoid any contact with water and other liquids, which will immediately dissolve it. Store away from moisture, heat sources, and direct sunlight. As a radioactive mineral, it requires careful handling – avoid inhaling dust and wash hands after each contact. ## Storage Línekite specimens must be stored in dry conditions, preferably in tightly sealed containers (e.g., "perky box" type) with a desiccant (silica gel). They should be protected from shocks and vibrations due to their extreme fragility.

Sources

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