Uramarsite
Chemical formula: N³⁻H₄(U⁶⁺O₂)As⁵⁺O₄·3H₂O
Uramarsite is a rare uranyl and arsenic mineral, forming bright green, tabular crystals with strong radioactivity.
Properties
- Mohs hardness
- 2.5
- Color
- Light green
- Luster
- Vitreous
- Streak
- White
- Density
- 3.22
- Cleavage
- perfect cleavage on {001} (less perfect on (010})
- Fracture
- Step-Like
- Transparency
- Translucent
- Crystal system
- Tetragonal
Diagnostic features
## Identification Key diagnostic features of uramarsite are its bright green color, tabular crystal habit, perfect cleavage, and strong radioactivity, easily detectable with a Geiger counter. It often also exhibits intense, green fluorescence under ultraviolet light. ## Distinguishing from Similar Minerals Uramarsite can be confused with other secondary uranium minerals from the autunite group, such as meta-autunite, metatorbernite, or metazeunerite. Distinguishing it from these minerals based on visual characteristics is very difficult and usually requires advanced chemical analyses (EDS) or X-ray diffraction (XRD) to confirm the presence of the ammonium group instead of calcium, copper, or zinc. ## Crystal Forms Uramarsite crystallizes as thin, square or rectangular tablets. These crystals often form fan-shaped, radial, or rosette-like aggregates and clusters. It also occurs as thin coatings and crusts on the host rock.
Geological environment
## Genesis Uramarsite is a secondary mineral that forms in the oxidation (weathering) zones of hydrothermal uranium deposits. It forms as a result of the action of waters rich in arsenic and ammonia on primary uranium minerals, such as uraninite. Ammonia can originate from the decomposition of organic matter in sedimentary rocks. ## Mineral Associations This mineral co-occurs with other secondary uranium and arsenic minerals. The most common associations include arsenuranospathite, uranospinite, metazeunerite, as well as gypsum and calcite. ## Localities The most important and also the type locality for uramarsite is the Bota-Burum uranium deposit in the Almaty region of Kazakhstan. This is the only confirmed and well-documented locality for this mineral in the world.
Rarity
Very rare
For collectors
## Quality Criteria The most valued specimens by collectors are those with well-formed, sharp crystals of intense, bright green color. Rich aggregates of crystals forming rosettes or fans on a small rock matrix are also highly prized. Due to the rarity of the mineral, even microscopic but well-formed crystals are considered valuable. ## Popular Localities The only source of collector specimens is its type locality – the Bota-Burum deposit in Kazakhstan. All specimens available on the market come from this single location.
Care and storage
## Cleaning Uramarsite specimens should not be cleaned wet. Any contaminants, such as dust, should be removed only with a soft brush or compressed air from a safe distance. Contact with water can lead to damage. ## What to Avoid Contact with water and chemicals must be strictly avoided. The mineral is sensitive to changes in humidity and temperature. As a uranium mineral, it is strongly radioactive – it requires special precautions. Direct skin contact should be avoided, dust should never be inhaled, and hands should always be washed after handling a specimen. ## Storage Uramarsite specimens must be stored in sealed, lead-lined or thick acrylic containers, clearly marked as radioactive material. These containers should be kept away from areas of permanent human habitation, as well as from other minerals that could be damaged by radiation.