Krásnoite

Chemical formula: Ca₃Al₇.₇Si₃P₄O₂₃.₅(OH)₁₂.₁F₂·₈H₂O

Krásnoite is an extremely rare phosphate mineral, occurring as microscopic, hexagonal crystals and spherical aggregates.

## Characteristics Krásnoite is a hydrated aluminum-calcium phosphate with additional fluoride and hydroxyl anions. It forms very small, hexagonal, tabular crystals up to 20 micrometers in size, which often combine into spherical aggregates reaching up to 0.2 mm in diameter. Due to the microscopic size of the crystals, its visual features are difficult to observe without specialized equipment. ## Physical Properties Due to the small size of its crystals, many physical properties of krásnoite have not been fully determined. Hardness and density are unknown. Its luster is described as vitreous. It is a transparent to translucent mineral. ## Colors and Varieties Observed specimens are colorless to white. No varieties of this mineral have been distinguished. ## History and Name The mineral was approved by the IMA in 2019 (IMA2019-061). Its name comes from its discovery locality – the town of Krásno in the Czech Republic, known for historical tin and tungsten mining. It was described by a team of mineralogists, including Jakub Plášil, who was the lead author of the publication. ## Uses Krásnoite has no industrial application and is solely an object of scientific interest and for specialized micromineral collectors.

Properties

Luster: Vitreous
Streak: White
Transparency: Transparent to translucent
Crystal system: Hexagonal

Diagnostic features

## Identification Identification of krásnoite is possible only through advanced analytical methods, such as X-ray diffraction (XRD) and chemical analysis (EDS/WDS). Visual identification in the field or even in a collection is impossible due to its microscopic size and lack of characteristic macroscopic features. ## Distinguishing from Similar Minerals It can be confused with many other secondary phosphate and sulfate minerals forming white coatings and aggregates, such as wavellite, crandallite, or cacoxenite. Definitive differentiation requires specialized laboratory analysis. ## Crystal Forms Krásnoite forms spherical aggregates composed of very small, hexagonal, tabular crystals. These crystals are radially oriented within the aggregates.

Geological environment

## Genesis Krásnoite is a secondary mineral that forms as a result of hydrothermal processes in the late stage of tin-tungsten greisen mineralization. It crystallizes in vugs in quartz, within altered (greisenized) granites. ## Mineral Associations This mineral co-occurs with quartz, fluorite, topaz, cassiterite, wolframite, apatite, wavellite, crandallite, cacoxenite, and minerals from the alunite group. ## Localities The only confirmed occurrence of krásnoite in the world is its type locality: the historical mining dump of the "Huber" tin mine (Huberův peň) in the town of Krásno, Karlovy Vary Region, Czech Republic.

Rarity

Extremely rare

For collectors

## Quality Criteria As a micromineral, the value of a specimen is primarily determined by the richness and quality of the spherical aggregates on the rock matrix. The most desirable samples are those with numerous, well-formed, and undamaged aggregates, clearly standing out from the substrate. The size of the aggregates (though still sub-millimeter) is also important. ## Popular Localities The only source of specimens is the type locality in Krásno, Czech Republic. Material from this location is extremely rare on the collector's market and mainly goes to scientific institutions and specialized micromineral collectors.

Care and storage

## Cleaning Specimens should be handled with the utmost care. Due to the microscopic size and fragility of the crystals, mechanical cleaning is impossible and not recommended. If dust removal is necessary, a gentle stream of compressed air can be used from a safe distance. ## What to Avoid Avoid contact with all chemicals, acids, and detergents. It should not be subjected to ultrasonic cleaning. As a hydrated mineral, it is potentially sensitive to high temperatures, which can lead to dehydration and destruction of its structure. ## Storage Krásnoite specimens should be stored in stable conditions, away from dust, moisture, and extreme temperatures. The safest storage method is a specialized micromount box, which protects delicate crystals from mechanical damage.

Sources

IMA Mineral List (CNMNC)