Calciodelrioite

Chemical formula: Ca(V⁵⁺O₃)₂·4H₂O

Calciodelrioite is a rare, hydrated calcium vanadate, forming transparent, tabular crystals with a vitreous luster.

## Characteristics Calciodelrioite is a hydrated calcium vanadate, belonging to the delrioite group. This mineral forms very small, bladed or tabular crystals, usually not exceeding 1 mm in length. It occurs as single crystals, rosette-like aggregates, or radial clusters. It is a secondary mineral, forming in the oxidation zones of uranium-vanadium deposits. ## Physical Properties Calciodelrioite crystals are transparent and exhibit a vitreous luster. The mineral is relatively soft, with a Mohs hardness of 2.5. It has a density of about 2.45 g/cm³, making it relatively light. It exhibits perfect cleavage in one direction. ## Colors and Varieties Calciodelrioite is usually colorless, but can range in color from light brown (tan) and brown to almost black. The coloration is likely due to impurities or inclusions. No named varieties have been distinguished. ## History and Name The mineral was described in 2017 by Anthony R. Kampf and his team. Its name refers to its chemical composition – the dominant calcium (Latin: *calcius*) – and its structural similarity to delrioite. It was approved by the International Mineralogical Association (IMA) under number 2017-023. The type locality is the West Sunday mine in the Slick Rock district, Colorado, USA. ## Uses Due to its rarity and microscopic crystal size, calciodelrioite has no industrial applications. It is solely an object of interest for collectors specializing in rare minerals or vanadium minerals.

Properties

Mohs hardness
2.5
Luster
Vitreous
Streak
White
Density
2.451
Cleavage
on {001} and possibly one or more additional cleavages parallel to [100].
Fracture
Irregular/Uneven,Splintery
Transparency
Transparent
Crystal system
Monoclinic

Diagnostic features

## Identification Calciodelrioite is difficult to identify visually due to the small size of its crystals. It is recognized by its characteristic habit of thin, bladed or tabular crystals, often forming radial aggregates. Its occurrence in paragenesis with other secondary vanadium and uranium minerals in sandstones is a key indicator. Final identification requires advanced analytical methods, such as X-ray diffraction (XRD) or chemical analysis (EDS). ## Distinguishing from Similar Minerals It can be confused with other secondary vanadate minerals, such as delrioite, metadelrioite, or pascoite. Delrioite contains strontium instead of calcium. Metadelrioite has a similar composition but a different crystal structure. Pascoite is distinguished by its intense orange or red color. Precise differentiation of these minerals in the field is practically impossible. ## Crystal Forms Crystals are thin, tabular or bladed, elongated along one axis. They often form fan-shaped, radial, or rosette-like aggregates, growing on the host rock.

Geological environment

## Genesis Calciodelrioite is a secondary mineral that crystallizes in the oxidation zones of uranium-vanadium deposits hosted in sandstones. It forms as a result of weathering processes of primary ore minerals under low temperature and pressure conditions, with the involvement of waters rich in dissolved vanadium and calcium. ## Mineral Associations This mineral co-occurs with other secondary vanadium and uranium minerals. At the type locality, it was found in association with minerals such as metarossite, pascoite, sherwoodite, as well as montroseite and corvusite. ## Localities The only confirmed and described occurrence of calciodelrioite in the world is its type locality: the West Sunday mine, located in the Slick Rock mining district, San Miguel County, Colorado, USA.

Rarity

Very rare

For collectors

## Quality Criteria The collector appeal of calciodelrioite specimens depends on several factors. Most valued are specimens with well-formed, sharp, and undamaged crystals, forming aesthetic, radial or rosette-like aggregates. A higher color contrast between colorless or light brown crystals and the dark host rock also enhances visual value. Due to their microscopic size, the quality of the entire mineral assemblage on the matrix is crucial. ## Popular Localities The only source of calciodelrioite specimens is its type locality: the West Sunday mine in Colorado, USA. All materials available on the collector market originate from this single location.

Care and storage

## Cleaning Specimens should be cleaned very carefully, using compressed air to remove dust. Due to the softness and fragility of the crystals, mechanical contact (e.g., with a brush) is highly inadvisable. If liquid is necessary, only isopropyl alcohol should be used in minimal amounts, avoiding water, which can damage the mineral. ## 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 Calciodelrioite specimens should be stored under stable conditions, preferably in sealed "micromount" containers or display cases with controlled humidity. Protect from dust, vibrations, and mechanical damage.

External references

Sources

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