Feynmanite
Chemical formula: Na(U⁶⁺O₂)(S⁶⁺O₄)(OH)·3.5H₂O
Feynmanite is a rare, secondary uranyl mineral, distinguished by its intense yellow color and occurrence as fine, acicular crystals.
Properties
- Mohs hardness
- 2
- Color
- Pale greenish yellow
- Luster
- Vitreous
- Streak
- White
- Density
- 3.324
- Cleavage
- {010}
- Fracture
- Irregular/Uneven
- Transparency
- Transparent
- Crystal system
- Monoclinic
Diagnostic features
## Identification Feynmanite can be identified by its characteristic bright yellow color, strong yellow-green fluorescence under UV light, and typical occurrence as fine, acicular crystals forming radial aggregates. Its presence in the oxidation zones of uranium deposits is a key indicator. ## Differentiation from Similar Minerals It can be confused with other secondary uranyl minerals of similar color and habit, such as uranophane, boltwoodite, or natrozippeite. Uranophane often forms larger, prismatic crystals. Natrozippeite tends to form earthy masses and coatings. Definitive differentiation of these minerals is usually only possible using advanced analytical methods, such as X-ray diffraction (XRD) or spectroscopy. ## Crystal Forms Crystals are very fine, acicular or bladed, elongated along the [010] axis. They usually form radial, stellate, or tangled aggregates.
Geological environment
## Genesis Feynmanite is a secondary mineral, formed in the oxidation (weathering) zones of uranium deposits. It crystallizes from waters rich in uranium, sodium, and sulfates under low temperature and pressure conditions. At the type locality (Red Canyon, Utah), it formed as a post-mining product on the walls of mine workings in sandstone containing uraninite and pyrite. ## Mineral Associations This mineral coexists with other secondary uranyl sulfates and silicates. At the type locality, it was found in association with gypsum, hexahydrite, metauranopilite, johannite, natrozippeite, as well as newly described minerals like redcanyonite and shumwayite. ## Localities The most important and type locality for feynmanite is the Blue Lizard mine in Red Canyon, White Canyon District, San Juan County, Utah, USA. This is currently the only confirmed locality for this mineral worldwide.
Rarity
Very rare
For collectors
## Quality Criteria The collector appeal of feynmanite depends on the richness and aesthetics of the crystal aggregates. The most prized specimens are those with well-formed, radial clusters of acicular crystals with an intense yellow color, clearly contrasting with the host rock. Due to the microscopic size of the crystals, specimens are primarily evaluated under magnification. Contrast with a dark rock matrix enhances visual value. ## Popular Localities The only source of feynmanite specimens is its type locality – the Blue Lizard mine in Red Canyon, Utah, USA. All specimens available on the collector market originate from this single location.
Care and storage
## Cleaning Feynmanite specimens should not be wet cleaned. The fine, acicular crystals are extremely delicate and fragile. Compressed air from a safe distance or a very soft brush can be used to remove dust, with utmost caution. ## What to Avoid Avoid contact with water and chemicals, which can dissolve or damage the delicate crystals. As a hydrated mineral, it is sensitive to changes in temperature and humidity, which can lead to dehydration and destruction. Ultrasonic cleaners and steam cleaning should be avoided. Due to its radioactivity, direct contact should be limited, and hands should always be washed after handling the specimen. ## Storage Specimens should be stored in stable conditions, away from heat sources and direct sunlight. The safest method is storage in a sealed, transparent "micromount" box, which protects delicate crystals from mechanical damage and dust, and also limits radiation exposure.