Hughesite
Chemical formula: Na₃Al[V⁵⁺₁₀O₂₈]·22H₂O
Hughesite is a very rare, water-soluble sodium and aluminum vanadate, forming aggregates of microscopic, bladed crystals with an intensely orange color.
Properties
- Mohs hardness
- 1
- Color
- Orange to golden orange
- Luster
- Vitreous
- Streak
- Yellow
- Density
- 2.29
- Cleavage
- One good direction of cleavage parallel to (001)
- Fracture
- Irregular/Uneven
- Transparency
- Transparent
- Crystal system
- Triclinic
Diagnostic features
## Identification Characteristic features of hughesite include its bright orange color, occurrence as small, bladed crystals forming crusts, and water solubility. The reaction to water is a key diagnostic feature. ## Distinguishing from Similar Minerals Hughesite can be confused with other secondary vanadium minerals of similar color, such as pascoite or lasalite. Pascoite crystallizes in the monoclinic system and has a slightly different chemical composition. Lasalite is also monoclinic and water-soluble, but differs from hughesite in the proportions of sodium and vanadium. Final distinction of these minerals requires advanced analytical methods, such as X-ray diffraction (XRD). ## Crystal Forms Hughesite forms very small, flattened, bladed crystals, elongated along one axis. These crystals typically occur in radial or chaotic aggregates, as well as in the form of thin crusts on the host rock (most often on sandstone).
Geological environment
## Genesis Hughesite is a secondary vanadium mineral that forms in the oxidation zone of uranium-vanadium deposits located in sandstones. It forms as a result of the weathering of primary vanadium minerals (e.g., montroseite) in desert conditions, with low humidity. Its formation is associated with the activity of groundwater rich in dissolved vanadates. ## Mineral Associations This mineral co-occurs with other secondary vanadates. In its type locality (West Sunday mine), it was found in association with minerals such as pascoite, lasalite, sherwoodite, as well as gypsum and quartz. ## Localities The only confirmed and described occurrence of hughesite in the world is its type locality - the West Sunday mine, located in the Slick Rock district, San Miguel County, Colorado, USA.
Rarity
Extremely rare
For collectors
## Quality Criteria The quality of hughesite specimens is primarily assessed based on the richness and aesthetics of the crust. The most valued specimens are those with dense, extensive aggregates of intensely colored, orange crystals that clearly contrast with the light host sandstone. Due to the microscopic size of the crystals, individual, well-formed crystals are not the main criterion for evaluation. The overall visual effect and rock surface coverage are what matter. ## Popular Localities All known collector specimens come from a single location in the world - the West Sunday mine in Colorado, USA. This is the only locality from which this mineral has been obtained, making it extremely important for collectors specializing in rare species or systematic minerals.
Care and storage
## Cleaning The mineral is water-soluble, so it must absolutely not be cleaned wet. Any contact with water, even distilled, will destroy the specimen. Cleaning can only be done dry, using compressed air to blow off dust. Extreme caution should be exercised due to the brittleness of the crystals. ## What to Avoid Avoid all contact with water and other liquids. The mineral is sensitive to atmospheric moisture, which can lead to its slow degradation. Protect it from high temperatures, which can cause loss of crystallization water and structural change. Avoid vibrations and impacts. ## Storage Hughesite specimens must be stored in a dry environment. The best solution is a sealed container (a "perky box") with a desiccant, such as silica gel. It should be stored at a stable temperature, away from direct sunlight.