Lehnerite
Chemical formula: Mn²⁺(U⁶⁺O₂)₂(PO₄)₂·8H₂O
Lehnerite is a rare, radioactive secondary mineral of the meta-autunite group, distinguished by its brownish-yellow color and tabular crystals.
Properties
- Mohs hardness
- 2-3
- Luster
- Vitreous, Pearly
- Streak
- pale yellow
- Density
- 3.50
- Cleavage
- Perfect on {010}; good on {101}; less good on <mi>{_101}</mi>; poor on {100}.
- Fracture
- Uneven
- Transparency
- Transparent,Translucent
- Crystal system
- Monoclinic
Diagnostic features
## Identification Lehnerite is identified by its characteristic brownish-yellow color, tabular crystal habit, and occurrence in paragenesis with other secondary uranium minerals. A key diagnostic feature is its strong radioactivity, easily detectable with a Geiger counter. Under shortwave UV light, it exhibits strong, greenish-yellow fluorescence. ## Distinguishing from Similar Minerals Lehnerite can be confused with other minerals from the meta-autunite group, such as meta-autunite or meta-torbernite. Distinguishing it from these often requires advanced chemical analyses (EDS) to confirm the presence of manganese as the dominant cation. Visually, it is almost identical to many related uranyl phosphates and arsenates. ## Crystal Forms Lehnerite crystals are thin, tabular, with a square or rectangular outline. They typically form fan-shaped, radial, or rosette-like aggregates, as well as thin coatings and crusts on the host rock.
Geological environment
## Genesis Lehnerite is a secondary mineral, forming in the oxidation (weathering) zones of uranium deposits, particularly in granitic pegmatites containing primary uranium minerals (e.g., uraninite) and phosphates (e.g., triplite). ## Mineral Associations This mineral co-occurs with other secondary uranium minerals, such as schoepite, paraschoepite, meta-autunite, meta-uranocircite, as well as with phosphates, e.g., strengite and phosphosiderite. ## Localities The most important and type locality for lehnerite is the Hagendorf South pegmatite in Bavaria, Germany. This is the only confirmed and well-documented locality for this mineral worldwide.
Rarity
Very rare
For collectors
## Quality Criteria The most prized lehnerite specimens are characterized by well-formed, sharp crystals forming aesthetic, fan-shaped or rosette-like aggregates. An intense, brownish-yellow color and contrast with the rock matrix are important. Due to its rarity, even microscopic but well-defined crystals are sought after by specialized collectors. ## Popular Localities The only source of collector specimens is the type locality – the Hagendorf South pegmatite in Bavaria (Germany). All specimens available on the market originate from this single location.
Care and storage
## Cleaning Lehnerite specimens should be cleaned only very carefully, using a soft brush to remove dust. Contact with water should be avoided, as it can damage the delicate crystals. Due to its radioactivity, all care activities should be performed with gloves. ## What to Avoid Contact with water and chemicals must be absolutely avoided. The mineral is sensitive to changes in temperature and humidity. It should not be exposed to direct sunlight, which can cause fading and dehydration. As a radioactive mineral, it should not be stored in areas of permanent human habitation. ## Storage Lehnerite must be stored in a sealed, lead-lined container with appropriate radioactivity warning labels. The container should be placed in a dry, cool, and dark place, away from other radiation-sensitive minerals. It should be kept out of reach of children and pets.