Parsonsite
Chemical formula: Pb<sup>2+</sup><sub>2</sub>(U<sup>6+</sup>O<sub>2</sub>)(PO<sub>4</sub>)<sub>2</sub>
Parsonsite is a rare, highly radioactive secondary mineral from the uranyl phosphate group, forming characteristic, fine crystals and coatings.
Properties
- Mohs hardness
- 2.5-3
- Luster
- Adamantine, Resinous, Greasy
- Streak
- Pale yellow
- Density
- 5.72-6.29
- Cleavage
- Good on {100}
- Fracture
- Uneven
- Transparency
- Transparent to Translucent
- Crystal system
- Triclinic
Diagnostic features
## Identification A key diagnostic feature is its very strong radioactivity, easily detectable with a Geiger counter. Visually, it is characterized by a pale yellow color, fine, tabular crystals forming rosettes, or earthy coatings. The lack of fluorescence under UV light is also an important clue. ## Distinguishing from Similar Minerals Parsonsite can be confused with other secondary uranium minerals, such as autunite or torbernite. However, autunite fluoresces strongly green under UV light, and torbernite contains copper and has a more greenish hue. Final differentiation often requires chemical analysis (XRD). ## Crystal Forms Crystals are usually very small, tabular, elongated in one direction. They often form radial or rosette-like aggregates. It also occurs as earthy, powdery masses, and as coatings and encrustations.
Geological environment
## Genesis Parsonsite is a secondary mineral, formed in the weathering (oxidation) zones of hydrothermal and sedimentary uranium deposits. It forms as a result of the alteration of primary uranium minerals, such as uraninite, in the presence of phosphate-rich waters. ## Mineral Associations It often co-occurs with other secondary uranium minerals, such as torbernite, autunite, kasolite, dewindtite, as well as with uraninite (as a primary mineral), quartz, feldspar, and clay minerals. ## Localities The most important and historical locality, from which the best specimens originate, is the Kasolo mine in Haut-Katanga Province, Democratic Republic of Congo. It is also known from the Ranger mine in the Northern Territory, Australia, from several locations in Germany (e.g., Wölsendorf in Bavaria), France (Lachaux in Auvergne), and the USA (e.g., in Utah).
Rarity
Rare
For collectors
## Quality Criteria The most sought-after specimens by specialized collectors are those with well-formed, visible crystals forming aesthetic, radial aggregates or rosettes on a contrasting rock matrix. The intensity and purity of the yellow color also increase the specimen's value. Due to the nature of the mineral, crystal size is usually small, so even millimeter-sized but sharp crystals are highly prized. ## Popular Localities Specimens from the type locality – the Kasolo mine in the Democratic Republic of Congo – are considered classic and most valuable. Good quality material also comes from the Ranger mine in Australia.
Care and storage
## Cleaning Due to its brittleness and potential for dusting, mechanical cleaning of specimens is not recommended. The safest method is to use canned compressed air to remove dust. Contact with water is inadvisable. ## What to Avoid It is absolutely essential to avoid inhaling mineral dust and direct skin contact. Washing hands after every contact is mandatory. Do not heat or expose the mineral to chemicals. Store away from moisture. ## Storage Parsonsite specimens must be stored in sealed, lead-lined or thick plastic containers, appropriately labeled as radioactive material. They should be kept away from areas of permanent human habitation, as well as away from other minerals that could be damaged by radiation (e.g., smoky quartz, fluorite).