Metadelrioite

Chemical formula: SrCa(V⁵⁺O₃)₂(OH)₂

Metadelrioite is a rare calcium strontium vanadate, forming microscopic, prismatic crystals with a vitreous luster.

## Characteristics Metadelrioite is a hydrated calcium strontium vanadate. It occurs as very small, prismatic or bladed crystals, rarely exceeding 0.5 mm in length. Crystals are typically colorless to white, sometimes with a pale yellow or greenish-yellow tint. They form radial aggregates, rosettes, or appear as single, disseminated crystals on the host rock surface. ## Physical Properties Metadelrioite crystals are characterized by a vitreous luster. They are transparent to translucent. The Mohs hardness is approximately 3. Due to the small size of the crystals, density is difficult to measure and has been calculated as 3.19 g/cm³. ## Colors and Varieties This mineral is most often colorless or white. Specimens with a pale yellow to greenish-yellow color are also found. No named varieties have been distinguished. ## History and Name Metadelrioite was first described in 1971 by Fabien Cesbron and Pierre H. Vachey. Its name refers to its structural and chemical similarity to the mineral delrioite, with the prefix "meta-" indicating a lower degree of hydration compared to delrioite. The name delrioite, in turn, comes from its discovery locality in Montrose County, Colorado, USA, near the Dolores River, whose Spanish name is "Rio de Nuestra Señora de los Dolores." ## Uses Metadelrioite has no industrial application. It is solely a mineral of scientific and collector interest, sought after by collectors specializing in rare minerals or vanadate minerals.

Properties

Mohs hardness
2
Color
Light yellow-green to darker green on exposed surfaces,
Luster
Vitreous
Streak
White
Density
4.3
Cleavage
Perfect on {010}
Fracture
Uneven
Transparency
Translucent
Crystal system
Triclinic

Diagnostic features

## Identification Metadelrioite is difficult to identify visually without magnification. It is recognized by its characteristic, tiny, prismatic or bladed crystals, often forming radial aggregates. Its occurrence in association with other secondary vanadium minerals on sandstones is a key indicator. ## Distinguishing from Similar Minerals It can be confused with other secondary vanadates, such as delrioite, metarossite, or pascoite. Delrioite forms similar aggregates but has a different chemical composition and a higher degree of hydration. Final differentiation from other rare vanadates requires advanced analytical methods, such as X-ray diffraction (XRD) or chemical analysis (EDS). ## Crystal Forms Crystals are elongated, prismatic, or bladed, often flattened. They typically form fan-like or radial aggregates and rosettes. Less commonly, they occur as single, isolated crystals.

Geological environment

## Genesis Metadelrioite is a secondary vanadium mineral that forms in the oxidation zones of uranium-vanadium deposits located in sedimentary rocks, mainly sandstones. It forms as a result of the weathering of primary vanadium minerals under low temperature and pressure conditions. ## Mineral Associations This mineral often co-occurs with other secondary vanadium and uranium minerals. The most common associations include: delrioite, metarossite, pascoite, hewettite, as well as montmorillonite, quartz, and calcite. ## Localities The most important and classic localities for metadelrioite are in the USA, in the Uravan Mineral Belt region of the Colorado Plateau. It has been found in mines in Montrose County, Colorado, and San Juan County, Utah. These are the main sources of specimens of this mineral.

Rarity

Very rare

For collectors

## Quality Criteria The most prized metadelrioite specimens are those with well-formed, sharp crystals creating aesthetic, radial aggregates or rosettes. A contrasting, dark rock matrix enhances the beauty of the white or pale yellow crystals. The size of the aggregates and the abundance of occurrence on the specimen also significantly increase its collector value. ## Popular Localities The best specimens come from historical localities in the USA, such as the Jo Dandy Mine in Montrose County, Colorado, which is the type locality for this mineral. Specimens from mines in the Paradox Valley area of Colorado and from San Juan County, Utah, are also highly valued by collectors.

Care and storage

## Cleaning Specimens should be cleaned very carefully, using a soft brush to remove dust. Due to their delicacy and small crystal size, washing with water should be avoided, especially ultrasonics, which can destroy aggregates. ## What to Avoid Avoid contact with acids and other chemicals. The mineral is relatively soft and brittle, so it must be protected from impacts and scratching. It should not be heated or exposed to sudden temperature changes. ## Storage It is recommended to store specimens in sealed "micromount" boxes, which protect them from dust, mechanical damage, and moisture. Avoid exposure to direct sunlight, although there is no evidence of fading.

External references

Sources

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