Libbyite
Chemical formula: (N<sup>3-</sup>H<sub>4</sub>)<sub>2</sub>(Na<sub>2</sub>☐)[(U<sup>6+</sup>O<sub>2</sub>)<sub>2</sub>(S<sup>6+</sup>O<sub>4</sub>)<sub>3</sub>(H<sub>2</sub>O)]<sub>2</sub>·7H<sub>2</sub>O
Libbyite is an extremely rare, radioactive secondary mineral from the uranyl sulfate group, distinguished by its intense yellow color and occurrence in uranium mines.
Properties
- Mohs hardness
- 2
- Luster
- Vitreous
- Streak
- Light yellow
- Density
- 3.13
- Cleavage
- Perfect on {010}
- Fracture
- Uneven
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
Diagnostic features
## Identification Key diagnostic features of libbyite are its lemon-yellow color, occurrence in the form of small, radial aggregates, and very strong, yellow-green fluorescence under UV light. Its strong radioactivity is also an important indicator. However, final identification requires advanced analytical methods, such as X-ray diffraction (XRD). ## Distinguishing from Similar Minerals Libbyite can be confused with other yellow secondary uranium minerals, such as uranophane, carnotite, or zippeite. Distinguishing it based on visual characteristics is practically impossible. Libbyite is distinguished by its unique chemical composition (presence of ammonium ions) and characteristic X-ray diffraction pattern. Unlike many of them, it is water-soluble. ## Crystal Forms Libbyite forms very small, prismatic crystals, elongated along the [100] axis. They most often occur as radial or spherulitic aggregates and rosettes, as well as coatings and crusts on the host rock.
Geological environment
## Genesis Libbyite is a secondary mineral, forming in the oxidation zones of uranium deposits. It forms as a result of the action of sulfate-rich waters on primary uranium-bearing minerals. Its formation is associated with weathering processes in mining environments, often as a post-mining product on tunnel walls and in mine workings. ## Mineral Associations This mineral co-occurs with other secondary sulfates and uranyl minerals. At the type locality (Peanut mine), it was found in association with gypsum, hexahydrite, natrozippeite, johannite, uranopilite, and nováčekite. ## Localities The only confirmed occurrence of libbyite in the world is its type locality – the Peanut mine, located in the Bull Canyon district, San Juan County, Utah, USA.
Rarity
Extremely rare
For collectors
## Quality Criteria The quality of libbyite specimens is primarily assessed based on the richness and aesthetics of the aggregates on the rock matrix. The most valued samples are those with clearly formed, spherical or radial clusters of intense, lemon-yellow color, contrasting with the substrate. Due to the microscopic size of the crystals, their individual form is not a key criterion. ## Popular Localities The only known and most valued specimens come from the Peanut mine in Utah, USA. This is the sole source of this mineral on the collector's market.
Care and storage
## Cleaning Libbyite specimens should generally not be wet cleaned. Due to its fragility and water solubility, the only safe method for dust removal is to use compressed air or a very soft brush. Contact with water and other liquids should be avoided. ## What to Avoid Libbyite is a strongly radioactive mineral – inhalation of dust and direct skin contact must be absolutely avoided. Washing hands after each contact is mandatory. The mineral is water-soluble. It should be protected from moisture, high temperatures, and direct sunlight, which can lead to its dehydration and decomposition. ## Storage Libbyite specimens must be stored in specialized, sealed, and appropriately labeled containers that protect against radiation. It is best to keep it away from other minerals, especially those sensitive to radiation, and in a dry place, away from heat and light sources.