Bobjonesite
Chemical formula: V<sup>4+</sup>OS<sup>6+</sup>O<sub>4</sub>·3H<sub>2</sub>O
Bobjonesite is a very rare, secondary vanadyl sulfate, forming aggregates of blue, acicular crystals.
Properties
- Mohs hardness
- 1
- Luster
- Vitreous
- Streak
- Light blue
- Density
- 2.25
- Cleavage
- Perfect on {010}
- Fracture
- Uneven
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
Diagnostic features
## Identification Bobjonesite can be identified by its characteristic, intensely blue color, acicular crystal form creating radial aggregates, and its occurrence in paragenesis with other secondary uranium and vanadium minerals. Its extreme softness (Mohs hardness 1) is also a diagnostic feature, although difficult to verify without damaging the specimen. ## Distinguishing from Similar Minerals Bobjonesite can be confused with other blue, secondary sulfates, such as chalcanthite or szomolnokite. It differs from chalcanthite by its crystal form (chalcanthite forms larger, prismatic crystals) and environment of occurrence (chalcanthite is a copper sulfate). From szomolnokite, which is an iron sulfate, it is distinguished primarily by its chemical composition, which requires advanced analyses (e.g., EDS). ## Crystal Forms This mineral forms very fine, acicular or bladed crystals, often flattened. These crystals combine into radial, stellate, or haphazardly tangled aggregates, and also form thin coatings and crusts on the host rock.
Geological environment
## Genesis Bobjonesite is a secondary mineral, forming in the oxidation zone of uranium-vanadium deposits in arid climates. It forms as a result of the weathering of primary vanadium minerals (e.g., montroseite) and sulfides (e.g., pyrite) under the influence of sulfuric acid-containing waters. It crystallizes on the walls of mine workings and on the surface of barren rocks as a product of post-silicification processes. ## Mineral Associations Bobjonesite co-occurs with other rare, secondary sulfate and vanadium minerals. It is most commonly associated with: stanleyite, szomolnokite, gypsum, metarossite, pascoite, rossite, and montroseite. ## Localities The most important and type locality for bobjonesite is the North Mesa Mine in the Temple Mountain area, Garfield County, Utah, USA. This is the only confirmed locality from which well-formed specimens of this mineral originate.
Rarity
Very rare
For collectors
## Quality Criteria The collector appeal of bobjonesite depends on several factors. Highly valued are specimens with rich, dense aggregates of well-formed, acicular crystals of intense blue color. Contrast with the rock matrix and the presence of associated minerals that confirm the paragenesis are also important. Due to the microscopic size of the crystals, specimens suitable for viewing under magnification are particularly sought after. ## Popular Localities The only source of bobjonesite collector specimens is its type locality - the North Mesa Mine in Utah, USA. All specimens available on the market come from this single location.
Care and storage
## Cleaning Bobjonesite specimens are extremely delicate and sensitive to water. Mechanical cleaning is impossible due to the fragility and small size of the crystals. Contact with any liquid should be avoided. The safest method for removing dust is to use a soft brush or carefully blow air from a safe distance. ## What to Avoid Contact with water, which can dissolve or damage the crystals, must be absolutely avoided. The mineral is sensitive to high temperatures and humidity changes, which can lead to its dehydration and destruction. It should be protected from chemicals, acids, and detergents. Due to its softness, any touching or rubbing should be avoided. ## Storage Bobjonesite specimens should be stored under stable conditions, in closed, airtight containers (e.g., "perky box" type), which protect against dust, moisture, and mechanical damage. It is recommended to store them in a dry place, away from direct sunlight and heat sources.