Magnesiopascoite

Chemical formula: Ca<sub>2</sub>Mg[V<sup>5+</sup><sub>10</sub>O<sub>28</sub>]·16H<sub>2</sub>O

Magnesiopascoite is a rare, orange-red vanadium mineral, forming characteristic rosette-like aggregates of tiny crystals.

## Characteristics Magnesiopascoite is a hydrated calcium and magnesium vanadate. It occurs as small, tabular or bladed crystals, which most often form radial, rosette-like, or spherulitic aggregates. Individual crystals rarely exceed 1 mm in length. These aggregates form thin crusts and coatings on host rocks, usually sandstones. ## Physical Properties Magnesiopascoite crystals exhibit an orange-red to orange-yellow color and a vitreous luster. The mineral is transparent to translucent. It is relatively soft, and its density is greater than that of typical rock-forming minerals. ## Colors and Varieties This mineral is uniform in color, ranging from orange-red to orange-yellow. No color or commercial varieties are distinguished. ## History and Name The name "magnesiopascoite" refers to its chemical composition (presence of magnesium) and structural similarity to the mineral pascoite. It was approved as a new mineral species by the International Mineralogical Association (IMA) in 1990. It was described based on samples collected from the Vanadium Queen uranium mine in San Juan County, Utah, USA. ## Uses Due to its rarity and microscopic crystal size, magnesiopascoite has no industrial application. It is of purely scientific and collector interest.

Properties

Mohs hardness
2.5
Luster
Vitreous
Streak
Orange-yellow
Density
2.5
Cleavage
Perfect on {010}
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Monoclinic

Diagnostic features

## Identification A characteristic feature of magnesiopascoite is its bright, orange-red, radial crystal aggregates on the host rock. Reaction to moisture (solubility in water) is also a key diagnostic feature, although destructive to the sample. ## Distinguishing from Similar Minerals It can be confused with other secondary vanadium minerals, such as pascoite or hewettite. Pascoite has a very similar appearance, but usually a lighter, more orange color and does not contain magnesium. Certain differentiation requires advanced chemical (EDS) or X-ray (XRD) analyses. ## Crystal Forms It forms elongated, tabular crystals, which almost always occur in radial or spherulitic aggregates and rosettes. Isolated, well-formed crystals are extremely rare.

Geological environment

## Genesis Magnesiopascoite is a secondary vanadium mineral. It forms in the oxidation zones of uranium-vanadium deposits, which occur in sedimentary rocks, mainly sandstones. It forms under arid climatic conditions as a result of the weathering of primary vanadium minerals. ## Mineral Associations It co-occurs with other vanadium minerals, such as hewettite, pascoite, as well as gypsum, montmorillonite, and other clay minerals. ## Localities The most important and classic locality, from which the best specimens originate, is the Vanadium Queen mine in the La Sal area, San Juan County, Utah, USA. This is the type locality for this mineral. It is also known from several other mines in the same Colorado Plateau region.

Rarity

Rare

For collectors

## Quality Criteria The most highly valued specimens are those with intensely colored, orange-red, well-formed, and distinct rosettes or spherulitic aggregates. Contrast with the light host rock (sandstone) and the size and coverage of the surface by crystal aggregates are important. Specimens without mechanical damage, with clear, lustrous crystals, are most desirable. ## Popular Localities By far the most known and valued specimens come from the type locality - the Vanadium Queen mine in Utah, USA. Specimens from this location are considered exemplary for the species.

Care and storage

## Cleaning Specimens should be cleaned only very carefully, using compressed air to remove dust. Contact with water is absolutely not recommended, as the mineral is soluble in it. ## What to Avoid Avoid contact with water, water vapor, and all liquids. Store away from high humidity environments, which can lead to chemical degradation and crystal disintegration. Protect from direct sunlight and high temperatures. ## Storage Magnesiopascoite specimens should be stored in sealed, transparent containers (so-called "perky boxes") or in display cases with humidity control. It is recommended to place a moisture-absorbing agent (e.g., silica gel) in the container.

External references

Sources

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