Donowensite

Chemical formula: Ca(H₂O)₃Fe³⁺₂(V⁵⁺₂O₇)₂

Donowensite is an extremely rare, orange-brown iron and calcium vanadate, forming microscopic, bladed crystals.

## Characteristics Donowensite is a hydrated iron and calcium vanadate, occurring as extremely small, bladed or tabular crystals, rarely exceeding 0.2 mm in length. These crystals form rosette-like or radial aggregates, as well as thin coatings and crusts on the surface of the host rock. Due to its microscopic size, its visual features are difficult to observe without magnification. ## Physical Properties Donowensite crystals exhibit an orange-brown color and a vitreous luster. They are transparent to translucent. Hardness and density have not been precisely measured due to the small size and rarity of the material. ## History and Name The mineral was named after Don Owens (born 1948), an American micromount mineral collector from Danville, Pennsylvania, who first discovered this mineral. It was approved by the International Mineralogical Association (IMA) in 2017 under number IMA2017-054. The discovery was made on material from the Packrat Mine in Gateway, Colorado, USA. ## Uses Donowensite has no industrial application. Its significance is purely scientific and collectible, as an extremely rare mineral species.

Properties

Mohs hardness
3
Color
Yellow
Luster
Vitreous
Streak
Orange
Density
2.97
Cleavage
on {001}; also very good on {100} and {010}
Fracture
Splintery
Transparency
Transparent to translucent
Crystal system
Triclinic

Diagnostic features

## Identification Identification of donowensite is practically possible only through advanced analytical methods, such as Raman spectroscopy or chemical analysis using an electron microprobe (EDS/WDS). Visually, under high magnification, characteristic orange-brown, bladed crystals forming rosette-like aggregates can be observed. ## Distinguishing from Similar Minerals It can be confused with other secondary vanadium minerals of similar color and habit, such as carnotite, tyuyamunite, or pascoite. Definitive distinction requires specialized chemical analysis to confirm the unique composition of donowensite. ## Crystal Forms Donowensite forms very small, thin, bladed crystals, elongated in one direction. These crystals often combine into radial or rosette-like aggregates, and also form thin coatings on the rock.

Geological environment

## Genesis Donowensite is a secondary mineral, formed in the oxidation zone of uranium-vanadium deposits. It forms as a result of weathering processes of primary vanadium minerals in a calcium-rich environment. It occurs in vugs and on fracture surfaces in sandstones. ## Mineral Associations This mineral co-occurs with other secondary vanadate minerals, such as carnotite, tyuyamunite, pascoite, as well as gypsum and montmorillonite. ## Localities The only confirmed locality of donowensite in the world (type locality) is the Packrat Mine, located in the Gateway area, Mesa County, Colorado, USA.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a donowensite specimen primarily depends on the richness and development of its microscopic crystals. Specimens with clearly formed, rosette-like aggregates of intense, orange-brown color, contrasting well with the host rock, are most valued. The absence of damage to the delicate crystals is also important. ## Popular Localities The only source of donowensite specimens is its type locality – the Packrat Mine in Colorado, USA. All specimens available on the collector's market originate from this single location.

Care and storage

## Cleaning Due to the extreme fragility and microscopic size of the crystals, mechanical cleaning is highly inadvisable. Specimens should be protected from dust by storing them in sealed containers. If cleaning is absolutely necessary, compressed air can be used from a very long distance and at low pressure. ## What to Avoid Avoid contact with water, chemicals, ultrasound, and all forms of mechanical cleaning (brushes, cloths). The crystals are extremely brittle and easily damaged or detached from the substrate. Rapid temperature changes should also be avoided. ## Storage Donowensite specimens should be stored exclusively in specialized "micromount" boxes that protect them from physical damage and dust. Vibrations and shocks should be avoided.

External references

Sources

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