Wernerbaurite

Chemical formula: (N³⁻H₄)₂Ca₂[V⁵⁺₁₀O₂₈]·16H₂O

Wernerbaurite is a very rare, hydrated calcium ammonium decavanadate, forming small, transparent crystals of intense, yellow-orange color.

## Characteristics Wernerbaurite is a vanadate mineral belonging to the pascoite family. It occurs as very small, tabular or bladed crystals, rarely exceeding 1 mm in length. It also forms radial and rosette aggregates. Its most characteristic feature is its intense, vivid, yellow-orange color. ## Physical Properties This mineral is very soft, with a Mohs hardness of 2. It is relatively light, with a density of 2.35 g/cm³. The crystals are transparent and exhibit a vitreous luster. Due to their small size and fragility, physical properties are studied on microscopic samples. ## Colors and Varieties Wernerbaurite occurs in a uniform, yellow-orange color. No color or commercial varieties are distinguished. ## History and Name The mineral is named in honor of Werner F. Baur (1930-2015), a German-American crystallographer and mineralogist from the University of Chicago, for his contributions to the study of mineral crystal structures. The mineral was approved by the International Mineralogical Association (IMA) in 2010. The type locality (first discovery) is the Saint Jude mine in the Slick Rock district, Colorado, USA. ## Uses Wernerbaurite has no industrial applications. Its significance is purely scientific and as a collector's item, as a unique and rare representative of vanadates.

Properties

Mohs hardness
2
Luster
Vitreous
Streak
Yellow
Density
2.352
Cleavage
{100} and {010}
Transparency
Transparent
Crystal system
Triclinic

Diagnostic features

## Identification Wernerbaurite is identified by its characteristic yellow-orange color, small, tabular crystals, and occurrence in paragenesis with other secondary vanadium minerals. Its low hardness and water solubility are key diagnostic features, although difficult to verify without destroying the sample. ## Distinguishing from similar minerals It can be confused with other secondary vanadium minerals of similar color, such as pascoite or huemulite. Pascoite usually has a more reddish-orange hue and forms crusts. Accurate differentiation of these minerals often requires advanced analytical methods, such as X-ray diffraction (XRD). ## Crystal forms Crystals are very small, typically tabular or bladed, flattened parallel to {001}. They often form fan-shaped or radial aggregates and small rosettes on the surface of the host rock.

Geological environment

## Genesis Wernerbaurite is a secondary vanadium mineral that forms in the oxidation zone of uranium-vanadium deposits hosted in sandstones. It forms as a result of weathering of primary vanadium minerals under low temperature and pressure conditions, in an arid climate. ## Mineral associations This mineral co-occurs with other secondary vanadate minerals, such as pascoite, huemulite, as well as gypsum, montmorillonite, and quartz. ## Localities The only confirmed and described occurrence of wernerbaurite in the world is its type locality - the Saint Jude mine, in the Slick Rock mining district, San Miguel County, Colorado, USA.

Rarity

Very rare

For collectors

## Quality criteria The quality of wernerbaurite specimens is assessed based on the size and habit of the crystals, their transparency, and the intensity of their color. The most prized specimens are those with clearly formed, undamaged crystals creating aesthetic aggregates on a small fragment of the host rock (matrix). The contrast of the mineral's color with a lighter sandstone background also enhances the specimen's attractiveness. ## Popular localities The only source of collector specimens is the Saint Jude mine in Colorado, USA. All samples available on the market come from this single locality, making them extremely rare and sought after by specialized collectors of rare minerals and micromounts.

Care and storage

## Cleaning Specimens should be cleaned only very carefully, using compressed air to remove dust. Any contact with water or other liquids is highly inadvisable, as the mineral is water-soluble. ## What to avoid Contact with water, acids, and other chemicals must be strictly avoided. The mineral is sensitive to changes in humidity and temperature. It should not be heated or exposed to direct sunlight, which can cause dehydration and destruction. ## Storage Wernerbaurite specimens must be stored in sealed, dry containers, preferably away from light sources and at a stable temperature. The use of specialized "micromount" boxes is recommended to protect delicate crystals from mechanical damage.

External references

Sources

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