Finchite

Chemical formula: Sr(U⁶⁺O₂)₂(V⁵⁺₂O₈)·5H₂O

Finchite is a rare, radioactive uranyl vanadate mineral characterized by its distinctive golden-yellow color and transparent, tabular crystals.

## Characteristics Finchite is a hydrated uranyl strontium vanadate belonging to the francevillite group. It forms very small, usually microscopic crystals with a tabular or bladed habit, often occurring as radial aggregates, rosettes, and spherulites. Its most characteristic feature is its intense, golden-yellow color. Due to its uranium content, it is a strongly radioactive mineral. ## Physical Properties This mineral is relatively soft, with a hardness of about 2 on the Mohs scale. It is quite heavy, with a density of approximately 4.35 g/cm³. Crystals exhibit perfect cleavage in one direction, corresponding to their tabular structure. The luster of finchite is described as vitreous to pearly on cleavage surfaces. It is transparent. ## Colors and Varieties Finchite occurs in a uniform, golden-yellow color. No color varieties or commercial varieties are distinguished. ## History and Name The mineral was named in honor of Warren I. Finch (1924–2009), a geologist with the United States Geological Survey (USGS), in recognition of his contributions to the study of uranium deposit geology. It was approved as a new mineral species by the International Mineralogical Association (IMA) in 2016. ## Uses Finchite has no industrial application. Its significance is purely scientific and as a collector's item, as a rare and well-defined secondary uranium mineral.

Properties

Mohs hardness
2
Luster
Vitreous
Streak
light yellow
Density
4.352
Cleavage
(001)
Fracture
Irregular/Uneven
Transparency
Transparent
Crystal system
Orthorhombic

Diagnostic features

## Identification Key diagnostic features of finchite include its characteristic golden-yellow color, crystal habit (small, tabular, often in radial aggregates), and strong radioactivity. The streak is light yellow. ## Distinguishing from Similar Minerals Finchite is visually very similar to other minerals in the francevillite group, such as francevillite and curite. Definitive differentiation requires advanced analytical methods, such as X-ray diffraction (XRD) or chemical analysis (EDS/WDS) to determine the dominant cation (strontium for finchite, barium for francevillite, lead for curite). ## Crystal Forms Crystals are very small, tabular, flattened parallel to (001). They usually form radial aggregates, rosettes, or spherulitic clusters on the surface of the host rock.

Geological environment

## Genesis Finchite is a secondary mineral, forming in the oxidation zones of uranium-vanadium deposits. It crystallizes under low-temperature conditions from solutions rich in uranium, vanadium, and strontium, typically in voids and fractures of sedimentary rocks, such as sandstones. ## Mineral Associations This mineral co-occurs with other secondary uranium and vanadium minerals. It is most commonly associated with tyuyamunite, carnotite, metatyuyamunite, as well as gypsum, barite, and calcite. ## Localities Finchite is a very rare mineral. It has been identified in two type localities in the USA: Sulfur Springs Draw in Texas and the Pandora mine in the La Sal district, Utah. These are the only confirmed occurrences worldwide.

Rarity

Very rare

For collectors

## Quality Criteria The most desirable finchite specimens are those with well-formed, sharp crystals creating aesthetic, radial aggregates or rosettes. The intensity and purity of the golden-yellow color also increase the specimen's value. Contrast with a dark host rock is an additional advantage. Due to the microscopic size of the crystals, specimens suitable for observation under magnification (so-called "micromounts") are standard. ## Popular Localities The only known sources of finchite specimens are its two type localities in the USA: the Pandora mine in Utah and Sulfur Springs Draw in Texas. Specimens from these locations are extremely rare and sought after by specialized collectors of uranium minerals.

Care and storage

## Cleaning Finchite specimens should not be cleaned wet. A soft brush or compressed air from a safe distance can be used to remove dust. Avoid skin contact and always wash hands after handling the mineral. ## What to Avoid As a strongly radioactive mineral, it requires special caution. Avoid inhaling dust and direct, prolonged contact. It should not be heated or exposed to chemicals. Store away from moisture, which can cause its degradation. ## Storage Finchite must be stored in a specialized, sealed, and appropriately labeled container, preferably with a lead lining, to minimize radiation. It should be kept away from other radiation-sensitive minerals and away from areas of permanent human habitation.

External references

Sources

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