Scenicite
Chemical formula: [(U⁶⁺O₂)(H₂O)₂(S⁶⁺O₄)]₂·3H₂O
Scenicite is a very rare, secondary uranyl mineral, forming transparent, bright greenish-yellow crystals and coatings, prized by specialized collectors.
Properties
- Mohs hardness
- 2
- Luster
- Vitreous
- Streak
- White
- Density
- 3.497
- Cleavage
- on {100}; also a good one, on {001}
- Fracture
- Irregular/Uneven
- Transparency
- Transparent
- Crystal system
- Orthorhombic
Diagnostic features
## Identification Scenicite can be recognized by its characteristic bright greenish-yellow color, vitreous luster, and typical forms of occurrence – small, acicular crystals forming radial aggregates or fibrous coatings. A key diagnostic feature is its strong radioactivity. ## Distinguishing from Similar Minerals Scenicite can be confused with other secondary uranium minerals of similar color, such as meta-autunite, uranophane, or zippeite. Distinguishing it often requires advanced analytical methods, such as X-ray diffraction (XRD). In field conditions, observing the crystal habit (small needles in radial aggregates) and knowing the associated minerals in a given locality can be helpful. ## Crystal Forms Scenicite crystals are very small, acicular or bladed, elongated along the [010] axis. They most often form radial, stellate, or spherical aggregates, as well as delicate, felt-like coatings on rock surfaces.
Geological environment
## Genesis Scenicite is a secondary mineral, forming in the oxidation zones of uranium deposits. It forms as a result of weathering and alteration of primary uranium minerals (such as uraninite) in the presence of sulfates, most often derived from the oxidation of pyrite or other sulfides. It forms as a product of post-depositional water activity in arid or semi-arid climates. ## Mineral Associations This mineral co-occurs with other secondary uranyl sulfates and silicates. In its type localities, it has been found in association with minerals such as gypsum, johannite, uranopilite, zippeite, and minerals from the boltwoodite group. ## Localities Scenicite is an extremely rare mineral. It has been identified in only two places in the world, which are its type localities: the Scenic Mine and the Green Lizard Mine, both located in San Juan County, Utah, USA.
Rarity
Extremely rare
For collectors
## Quality Criteria The most highly valued scenicite specimens are those with well-formed, distinct crystals that create aesthetically pleasing, radial aggregates on a contrasting rock matrix. The intensity and purity of the bright greenish-yellow color also contribute to the specimen's attractiveness. Due to the microscopic size of the crystals, the richness of the coating and its surface area are key evaluation factors. ## Popular Localities The only known source of scenicite specimens are two mines in San Juan County, Utah, USA – the Scenic Mine and the Green Lizard Mine. Specimens from these localities are highly sought after by collectors specializing in mineral systematics and uranium minerals.
Care and storage
## Cleaning Scenicite specimens are extremely delicate and fragile. Mechanical cleaning should be avoided. If absolutely necessary, a stream of compressed air can be used from a safe distance to remove dust. Contact with water, which can damage or dissolve the mineral, should be avoided. ## What to Avoid The mineral is sensitive to moisture, temperature changes, and direct sunlight. Contact with chemicals and acids must be strictly avoided. Due to its fragility, vibrations and shocks should be prevented. ## Storage Scenicite specimens should be stored under stable conditions, preferably in closed, padded "micromount" boxes that protect them from mechanical damage, dust, and moisture. Due to its radioactivity, it should be stored away from areas of permanent human presence, in accordance with safety regulations for uranium minerals.