Thorasphite

Chemical formula: Th₄+₂H(As₅+O₄)₂(PO₄)·₆H₂O

Thorasphite is an extremely rare, radioactive thorium arsenate-phosphate, forming microscopic, colorless tabular crystals.

## Characteristics Thorasphite is a hydrated thorium arsenate-phosphate. It occurs as extremely small, tabular crystals not exceeding 100 micrometers in size, forming aggregates and rosettes. The crystals are colorless and transparent, with a vitreous luster. ## Physical Properties Due to the microscopic size of the crystals, most physical properties, such as hardness, density, cleavage, or fracture, have not been determined. The mineral is highly radioactive due to its high thorium content. ## History and Name The mineral's name refers to its chemical composition – the dominant thorium (Latin: *thorium*) and the presence of arsenate (As) and phosphate (P) groups. It was approved as a new mineral by the IMA in 2023 (IMA2023-043).

Properties

Luster: Vitreous
Streak: White
Transparency: Transparent
Crystal system: Triclinic

Diagnostic features

## Identification Identification is only possible using advanced analytical methods, such as energy-dispersive X-ray spectroscopy (EDS/WDS) to determine chemical composition and X-ray diffraction (XRD) for crystal structure analysis. Visual identification is impossible. ## Distinguishing from Similar Minerals Due to its unique chemical composition (a combination of thorium, arsenic, and phosphorus), it is easy to distinguish from other minerals at an analytical level. It occurs in association with other rare secondary minerals, which can help guide research. ## Crystal Forms It forms very small, thin tabular crystals, often grouped into rosettes or irregular aggregates.

Geological environment

## Genesis Thorasphite is a secondary mineral that formed as a result of weathering and alteration of primary thorium- and arsenic-bearing minerals in the oxidation zone of a polymetallic deposit. Its crystallization occurred under low-temperature conditions from solutions rich in arsenic, phosphorus, and thorium. ## Mineral Associations This mineral occurs in direct association with other secondary arsenates, such as arsenogoyazite, beudantite, mimetite, agardite-(Y), and with quartz. ## Localities The only known occurrence (type locality) is the historic uranium mine Schmiedestollen, located in Wittichen in the Black Forest, Baden-Württemberg, Germany.

Rarity

Extremely rare

For collectors

## Quality Criteria As a mineral of purely scientific and typological significance, its collector value is practically zero. Specimens are microscopic and visually unattractive. The only value lies in the fact of possessing a documented specimen from the type locality, which is, however, limited to specialized research institutions due to radioactivity and extreme rarity.

Care and storage

## Cleaning Due to its extreme rarity, microscopic size, and fragility, specimens should not be cleaned mechanically or chemically. ## What to Avoid Any contact with chemicals, ultrasound, and temperature changes should be avoided. As a highly radioactive mineral, it requires specialized precautions and should not be handled without appropriate knowledge and protective equipment. ## Storage Specimens must be stored in specialized, lead-lined containers designed for radioactive materials, away from other minerals that could be damaged by radiation. Storage requires strict adherence to regulations concerning radioactive materials.

Sources

IMA Mineral List (CNMNC)