Meisserite
Chemical formula: Na<sub>5</sub>(U<sup>6+</sup>O<sub>2</sub>)(S<sup>6+</sup>O<sub>4</sub>)<sub>3</sub>(S<sup>6+</sup>O<sub>3</sub>OH)·H<sub>2</sub>O
Meisserite is a very rare, water-soluble uranyl sulfate, forming tiny, yellow crystals on uranium mine dumps.
Properties
- Mohs hardness
- 2
- Luster
- Vitreous
- Streak
- Light yellow
- Density
- 3.33
- Cleavage
- Perfect on {010}
- Fracture
- Uneven
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
Diagnostic features
## Identification Key diagnostic features of meisserite include its pale yellow color, strong yellow-green fluorescence under UV light, and water solubility. Its occurrence as small, tabular crystals in paragenesis with other secondary uranium minerals is also characteristic. ## Differentiation from Similar Minerals Meisserite can be confused with other secondary uranyl sulfates, such as johannite or natrozippeite. Final differentiation requires advanced analytical methods, such as Raman spectroscopy or X-ray diffraction (XRD). Under collecting conditions, a water solubility test (on a micro-fragment) can be helpful, although it is a destructive method. ## Crystal Forms Meisserite forms very small, thin, tabular crystals with a lath-like habit, often elongated. These crystals combine into small, radial or rosette-like aggregates, and also form thin coatings on the host rock.
Geological environment
## Genesis Meisserite is a secondary mineral, formed by the weathering of uranium minerals (mainly uraninite) in a sulfate-rich environment. It forms as a post-mining product on dumps and in old workings of uranium mines, where waters rich in sulfuric acid (formed from pyrite oxidation) react with uranium minerals. ## Mineral Associations This mineral co-occurs with other secondary uranyl sulfates and uranium minerals. In the type locality (Schmiedersfelde), it was found in association with gypsum, johannite, uranopilite, zippeite, and natrozippeite. ## Localities Meisserite is an extremely rare mineral. Besides the type locality in Schmiedersfelde, Germany, its occurrence has only been confirmed at the Give-a-way-Elke mine in the North Flinders Ranges, South Australia.
Rarity
Very rare
For collectors
## Quality Criteria For meisserite, the most important criterion is the richness and aesthetics of crystal aggregates on the rock matrix. Specimens with clearly visible, well-formed rosette aggregates are sought after. The intensity of the yellow color and the contrast with the dark host rock also increase the specimen's value. Due to the microscopic size of the crystals, quality assessment often requires magnification. ## Popular Localities The only source of specimens available on the collector's market is the type locality – the mine dumps in Schmiedersfelde, Germany. Specimens from this locality are considered the best and most representative for this mineral.
Care and storage
## Cleaning The mineral is water-soluble, so it must absolutely not be cleaned wet. Specimens should only be dry-cleaned, using compressed air to remove dust. Due to its brittleness, touching the crystals should be avoided. ## What to Avoid Water and all liquids (alcohol, acids) will immediately dissolve and destroy the mineral. High humidity should be avoided, as it can lead to its slow degradation. Due to radioactivity, direct exposure should be limited, and hands should always be washed after contact with the specimen. ## Storage Meisserite specimens must be stored in a dry, tightly sealed container, preferably with a desiccant (e.g., silica gel). They should be kept away from other minerals that could be damaged by its radioactivity. Store in a place inaccessible to children and pets.