Chenowethite
Chemical formula: Mg(H₂O)₆[(U⁶⁺O₂)₂(S⁶⁺O₄)₂(OH)₂]·5H₂O
Chenowethite is a very rare, water-soluble uranyl mineral with an intensely yellow color, occurring as fine, acicular crystals.
Properties
- Mohs hardness
- 2
- Color
- pale green yellow
- Luster
- Vitreous
- Streak
- white
- Density
- 3.05
- Cleavage
- two cleavages: {010} perfect and {001} good
- Fracture
- Splintery,Step-Like
- Transparency
- Transparent
- Crystal system
- Orthorhombic
Diagnostic features
## Identification Key diagnostic features of chenowethite include its intense yellow color, acicular or bladed crystal habit forming radial aggregates, and strong green fluorescence under UV light. Its water solubility is also an important indicator. ## Distinguishing from Similar Minerals Chenowethite can be confused with other yellow secondary uranium minerals, such as zippeite, johannite, or uranophane. Distinguishing it from zippeite, with which it often co-occurs, is particularly difficult and usually requires advanced analytical methods, such as Raman spectroscopy or X-ray diffraction (XRD). A hint may be a slightly brighter, lemon-yellow hue compared to the more orange-yellow zippeite. ## Crystal Forms The mineral forms very small, elongated crystals with an acicular or bladed habit. These crystals combine into radial, stellate, or spherical aggregates, and also form delicate, felted crusts on rock surfaces.
Geological environment
## Genesis Chenowethite is a secondary mineral, forming in the oxidation zone of uranium deposits. It forms as a result of the weathering of primary minerals, such as uraninite, in the presence of sulfate-rich waters. It occurs as a post-mining product on the walls of mine workings, where it crystallizes from aqueous solutions under conditions of low temperature and rapid evaporation. ## Mineral Associations This mineral co-occurs with other secondary sulfates and uranyl minerals. It is most often accompanied by gypsum, zippeite, johannite, natrozippeite, as well as newly described minerals from the same locality, such as bluelizardite, redcanyonite, and greenlizardite. ## Localities The only confirmed occurrence (type locality) of chenowethite is the Blue Lizard mine, located in Red Canyon, San Juan County, Utah, USA. This is a classic locality for many rare secondary uranium minerals.
Rarity
Very rare
For collectors
## Quality Criteria The most prized chenowethite specimens are those that have well-formed, distinct aggregates of acicular crystals with an intense, pure color. Contrast with a dark host rock significantly enhances visual appeal. Due to the microscopic size of the crystals, specimens are primarily evaluated under magnification. Association with other rare uranyl minerals is also important. ## Popular Localities The only source of chenowethite specimens is its type locality – the Blue Lizard mine in Utah, USA. Material from this location is highly sought after by collectors specializing in mineral systematics and uranium minerals.
Care and storage
## Cleaning Chenowethite specimens must absolutely not be wet-cleaned. The mineral is water-soluble, and contact with water, even in the form of humid air, can damage or destroy it. To remove dust, only use compressed air from a safe distance or a very soft brush, with the utmost caution. ## What to Avoid Avoid contact with water, all chemicals, and high air humidity. The mineral is very fragile and sensitive to shocks and temperature changes. As a uranium mineral, it is radioactive and requires safe handling – avoid inhaling dust and wash hands after each contact. ## Storage Chenowethite must be stored in a dry place, preferably in a sealed, transparent container (a "micromount box") with a desiccant. Exposure should be away from direct sunlight and heat sources. Due to radioactivity, specimens should be stored away from areas of permanent human habitation.