Deliensite
Chemical formula: Fe<sup>2+</sup>(U<sup>6+</sup>O<sub>2</sub>)<sub>2</sub>(S<sup>6+</sup>O<sub>4</sub>)<sub>2</sub>(OH)<sub>2</sub>·7H<sub>2</sub>O
Deliensite is a very rare, secondary uranyl mineral, forming aggregates of small, platy crystals with an intense yellow color.
Properties
- Mohs hardness
- 2
- Luster
- Vitreous
- Streak
- Light yellow
- Density
- 3.17
- Cleavage
- Perfect on {001}
- Fracture
- Micaceous
- Transparency
- Transparent to Translucent
- Crystal system
- Orthorhombic
Diagnostic features
## Identification Identification of deliensite is based on its characteristic, intense yellow color, its occurrence as small, platy crystals forming rosette-like aggregates, and its geological environment – oxidation zones of uranium deposits. The mineral exhibits strong, green fluorescence under ultraviolet light (both shortwave and longwave). ## Distinguishing from Similar Minerals Deliensite can be confused with other yellow secondary uranyl minerals, such as uranophane, boltwoodite, or zippeite. Distinguishing it from these minerals often requires advanced analytical methods, such as X-ray diffraction (XRD). Observation of crystal form under a microscope can be helpful – deliensite forms characteristic, thin plates. ## Crystal Forms Deliensite crystals are very small, thin, and platy, with a rhombic outline. They typically occur as radial or rosette-like aggregates, as well as thin crusts on the host rock.
Geological environment
## Genesis Deliensite is a secondary mineral, formed as a result of weathering and oxidation of primary uranium ores (mainly uraninite) in the presence of iron sulfides (e.g., pyrite). It crystallizes from aqueous solutions under low temperature and pressure conditions, in a sulfate-rich environment. ## Mineral Associations This mineral co-occurs with other secondary uranium minerals. In its type locality (Shinkolobwe), it was found in association with gypsum-selenite, uraninite, and also minerals from the boltwoodite and uranophane groups. ## Localities The most important and type locality for deliensite is the Shinkolobwe mine in Haut-Katanga Province, Democratic Republic of Congo. This is the only confirmed and well-documented locality for this mineral worldwide.
Rarity
Very rare
For collectors
## Quality Criteria The most highly prized deliensite specimens are those that possess rich, well-formed crystal aggregates of an intense, lemon-yellow color, contrasting with the host rock. Due to the microscopic size of the crystals, their abundance and the aesthetics of the entire aggregate are key. Specimens from the well-defined type locality (Shinkolobwe) are particularly sought after. ## Popular Localities The only source of collector specimens is the historic Shinkolobwe mine in the Democratic Republic of Congo. Material from this location is extremely difficult to obtain, as the mine has long been closed and inaccessible.
Care and storage
## Cleaning Deliensite specimens should not be wet cleaned. Only gentle dust removal with a soft brush or a photographic air blower is permissible. Any contact with water or other liquids can lead to the dissolution and destruction of the mineral. ## What to Avoid Absolutely avoid contact with water, chemical agents, and sudden changes in temperature and humidity. Deliensite is an unstable mineral under conditions other than those prevailing in a dry environment. As a uranium mineral, it exhibits radioactivity, so direct exposure should be limited, and it should be stored away from areas of permanent human presence. ## Storage Specimens should be stored in tightly sealed, transparent containers (perky boxes) that protect them from dust, mechanical damage, and humidity changes. Containers should be clearly labeled as containing a radioactive mineral.