Schubnelite

Chemical formula: Fe³⁺V⁵⁺O₄·H₂O

A rare hydrated iron vanadate, forming small, black crystals with a strong luster, found in the oxidation zones of uranium-vanadium deposits.

## Characteristics Schubnelite is a hydrated iron vanadate, occurring extremely rarely. It forms very small, tabular or bladed crystals, which rarely exceed 0.5 mm in length. It is most often observed as radial or stellate aggregates, as well as crusts and coatings. Its characteristic features are an intense black color and a strong, almost metallic luster, which gives it an impressive appearance despite its small size. ## Physical Properties Schubnelite crystals are brittle. They exhibit a strong, almost metallic to adamantine luster. They are translucent, and their very thin fragments appear yellowish-brown to greenish-brown. The mineral's density is approximately 3.28 g/cm³. ## Colors and Varieties This mineral is monochromatic – it occurs exclusively in a shiny black color. No color or commercial varieties are distinguished. ## History and Name Schubnelite was first described in 1970 by Fabien Cesbron and Henri Vachey. The mineral is named in honor of Henri-Jean Schubnel (born 1935), a French mineralogist and curator of the mineral collection at the National Museum of Natural History in Paris. The type locality, from which the first described specimens originated, is the Mounana uranium mine in Gabon. ## Applications Schubnelite has no industrial applications. Its significance is purely scientific and collectible due to its extreme rarity and attractive microcrystals.

Properties

Luster
Adamantine to Sub-Metallic
Density
3.28
Transparency
Translucent
Crystal system
Triclinic

Diagnostic features

## Identification Schubnelite can be recognized by its characteristic, small, black crystals with a tabular habit, often forming radial or stellate aggregates. A key feature is its very strong, almost metallic luster. It occurs in a specific environment – the oxidation zones of vanadium deposits. ## Distinguishing from Similar Minerals It can be confused with other black, shiny secondary minerals, such as some manganese oxides (e.g., pyrolusite, hollandite) or other rare vanadates. It is distinguished from manganese oxides by its crystal form (thin tablets) and its association with other vanadium minerals. Definitive identification requires advanced analytical methods, such as XRD or EDS, due to the small size of the crystals. ## Crystal Forms Crystals are very small, usually tabular or bladed, flattened. They often form fan-shaped, radial, or stellate aggregates and clusters. It also occurs as fine crusts on the host rock.

Geological environment

## Genesis Schubnelite is a secondary mineral formed in the oxidation zones of hydrothermal uranium-vanadium deposits. It crystallizes from vanadium- and iron-rich solutions under low temperature and pressure conditions, often in voids and fractures of sedimentary rocks, such as sandstones. ## Mineral Associations This mineral co-occurs with other secondary vanadium and uranium minerals. At the type locality (Mounana, Gabon), it was found in association with francevillite, chervetite, curienite, as well as goethite and various manganese oxides. ## Localities The most important and classic occurrence of schubnelite is its type locality – the Mounana mine in Haut-Ogooué Province, Gabon. This is the only place from which well-formed, collectible specimens of this mineral originate. Its occurrence has also been confirmed in several other locations worldwide, but these are mostly trace amounts of purely scientific significance.

Rarity

Very rare

For collectors

## Quality Criteria The quality of a schubnelite specimen primarily depends on the abundance and form of its crystals. Most prized are specimens with distinct, radial or stellate aggregates of black, shiny crystals, sharply contrasting with the host rock. The size of the aggregates and the absence of mechanical damage significantly increase collectible value. Contrast with colorful associated minerals (e.g., yellow francevillite) is also highly desirable. ## Popular Localities The only source of collectible specimens is the historic locality at the Mounana mine in Gabon. This mine has long been inactive, meaning new specimens do not appear on the market. All available specimens come from old collections, which further increases their value and rarity.

Care and storage

## Cleaning Schubnelite specimens are extremely delicate and small. They should only be cleaned with compressed air from a safe distance to remove dust. Any contact with water, and especially with chemicals, is absolutely not recommended. Do not use brushes or ultrasonics. ## What to Avoid Avoid contact with water and any liquids that could dissolve or damage the delicate crystals. The mineral is brittle, so it must be protected from shocks, impacts, and abrasion. Store away from heat sources and extreme temperature changes. ## Storage The best way to store it is in a sealed, lidded "micromount" box, which protects the specimen from dust, moisture, and mechanical damage. Display should only be in enclosed display cases, away from direct sunlight and sources of vibration.

External references

Sources

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