Lepersonnite-(Gd)
Chemical formula: [Ca<sub>0.5</sub>Gd<sub>0.5</sub>(H<sub>2</sub>O)<sub>18</sub>(OH)<sub>1.5</sub>][Gd(U<sup>6+</sup>O<sub>2</sub>)<sub>12</sub>(SiO<sub>3</sub>OH)<sub>2</sub>(CO<sub>3</sub>)<sub>4</sub>(OH)<sub>10</sub>O<sub>2</sub>(H<sub>2</sub>O)<sub>5</sub>]
Lepersonnite-(Gd) is an extremely rare, radioactive uranyl and gadolinium mineral, forming yellow, spherical aggregates and acicular crystals.
Properties
- Mohs hardness
- 2-3
- Luster
- Silky
- Streak
- Light yellow
- Density
- 3.98
- Cleavage
- Perfect on {100}
- Fracture
- Uneven
- Transparency
- Translucent
- Crystal system
- Orthorhombic
Diagnostic features
## Identification Lepersonnite-(Gd) can be identified by its characteristic, intensely yellow color and typical occurrence as small, spherical aggregates composed of very fine, acicular crystals. Strong radioactivity is a key diagnostic feature. ## Distinguishing from Similar Minerals It can be confused with other secondary uranium minerals of similar color and form, such as studtite, metaschoepite, or rutherfordine. Definitive differentiation requires advanced analytical methods, such as X-ray diffraction (XRD) or chemical analysis (EDS), to confirm the presence of gadolinium, silicon, and carbonate in the structure. ## Crystal Forms Crystals are very fine, acicular or capillary, elongated along the [001] axis. They typically form radial, spherical aggregates (spherulites) or coatings and encrustations on other minerals.
Geological environment
## Genesis It is a secondary mineral, forming in the oxidation zones of uraninite deposits. It forms as a result of weathering and alteration of primary uranium ores in the presence of waters rich in carbonates, silica, and rare earth elements, especially gadolinium. ## Mineral Associations It co-occurs with other secondary uranium minerals, such as schoepite, becquerelite, curite, rutherfordine, as well as with uraninite (as a primary mineral) and quartz. ## Localities The most important and type locality for this mineral is the Shinkolobwe mine in Haut-Katanga Province, Democratic Republic of Congo. This is the only confirmed locality from which well-characterized specimens originate.
Rarity
Very rare
For collectors
## Quality Criteria The collector appeal of lepersonnite-(Gd) depends on the intensity and purity of its yellow color, as well as the size and good development of its spherical aggregates. Specimens where spherical aggregates are clearly separated and deposited on a contrasting substrate (matrix) are most valued. Due to the microscopic size of the crystals, their individual forms are not a criterion for evaluation. ## Popular Localities The only source of collector specimens is the historical locality – the Shinkolobwe mine in the Democratic Republic of Congo. This mine is currently closed and inaccessible, meaning no new specimens enter the market, making historical material extremely valuable.
Care and storage
## Cleaning Specimens should not be wet cleaned. To remove dust, a soft brush or compressed air from a safe distance can be used to avoid damaging the fragile crystals. ## What to Avoid Contact with water, chemicals, and acids, which can destroy the mineral, must be strictly avoided. As a secondary mineral, it is unstable and sensitive to changes in humidity. Due to its strong radioactivity, exposure should be limited, and hands should always be washed after handling the specimen. ## Storage Store in a dry place, preferably in a sealed, closable "membrane box" to protect delicate structures from mechanical damage and vibrations. It should be kept away from other radiation-sensitive minerals and stored in a location isolated from permanent human presence, with appropriate radioactivity labeling.