Burroite
Chemical formula: (N<sup>3-</sup>H<sub>4</sub>)<sub>2</sub>Ca<sub>2</sub>[V<sup>5+</sup><sub>10</sub>O<sub>28</sub>]·15H<sub>2</sub>O
Burroite is a very rare, hydrated calcium and ammonium vanadate, forming efflorescent coatings that are yellow-green to olive-green in color.
Properties
- Mohs hardness
- ~2
- Luster
- Vitreous, Pearly
- Streak
- Pale green
- Density
- 2.41
- Cleavage
- Perfect on {010}
- Transparency
- Translucent
- Crystal system
- Triclinic
Diagnostic features
## Identification The characteristic features of burroite are its mode of occurrence (efflorescent, felted coatings), its specific yellow-green to olive color, and its geological environment. It occurs on the walls of mine workings in sandstone. Its softness and fragility are also important diagnostic clues. However, definitive identification requires advanced analytical methods, such as chemical analysis (EDS) or X-ray diffraction (XRD). ## Distinguishing from Similar Minerals Burroite can be confused with other secondary vanadium minerals of similar colors, such as pascoite, huemulite, or some uranyl minerals (e.g., carnotite). It is distinguished by the presence of ammonium ions in its structure, the specific bladed habit of its crystals (visible under magnification), and perfect cleavage. Co-occurrence with other vanadates is typical, but precise differentiation in field conditions is practically impossible. ## Crystal Forms It forms aggregates of very small, bladed crystals that arrange themselves into matted or felted aggregates. It also occurs as crusts and coatings on the parent rock.
Geological environment
## Genesis Burroite is a secondary mineral that forms under supergene conditions. It forms as a product of the weathering of primary vanadium ores. Its formation is observed as a contemporary efflorescence on sandstone walls in dry mine workings, resulting from the interaction of water and air with primary minerals. ## Mineral Associations This mineral occurs in association with other vanadium minerals. The most common associations include corvusite, montroseite, pascoite, huemulite, and gypsum. ## Localities The only confirmed locality of burroite in the world is its type locality – the Burro mine, in the Slick Rock district, San Miguel County, Colorado, USA.
Rarity
Extremely rare
For collectors
## Quality Criteria The quality of a burroite specimen, usually a micromineral, is assessed based on several criteria. The most important is the abundance and saturation of the coating's color on the parent rock (matrix). Specimens on which well-formed, though tiny, bladed crystals are visible under magnification are more highly valued. The presence of rare associated minerals on the same rock fragment also enhances its attractiveness. ## Popular Localities The only source of burroite specimens is its type locality in Colorado, USA. All materials available on the collector's market come from this single mine.
Care and storage
## Cleaning Burroite specimens are extremely delicate and sensitive. Cleaning should be kept to an absolute minimum. Only very careful removal of dust with a stream of compressed air from a distance or using an exceptionally soft brush (e.g., squirrel hair) is permissible. Any contact with water and other liquids should be avoided. ## What to Avoid As a hydrated and efflorescent mineral, burroite is sensitive to changes in humidity and temperature. Contact with water, which can dissolve or damage it, must be strictly avoided. It should not be heated or exposed to dry air, as this can lead to the loss of water from its structure and disintegration. It should be protected from chemicals, ultrasound, and mechanical damage. ## Storage It is recommended to store specimens in tightly sealed containers (e.g., "perky boxes"), which help maintain a stable microclimate and protect against dust and damage. Exposure should be away from direct sunlight and heat sources.