Fervanite

Chemical formula: Fe₃+₄V₅+₄O₁₆·₅H₂O

Fervanite is a rare, hydrated iron vanadate, forming characteristic fibrous aggregates of golden-brown or yellowish-brown color.

## Characteristics Fervanite is a rare mineral from the vanadate group, chemically a hydrated iron(III) vanadate. It usually occurs as fibrous aggregates, radial clusters, or felted masses. Less commonly, it forms rosette-like or spherulitic (spherical) shapes. Individual crystals are very fine, acicular or bladed, and rarely visible to the naked eye. Its name refers to its chemical composition. ## Physical Properties This mineral is characterized by a silky or pearly luster on cleavage surfaces, and in mass, it can be dull or earthy. It is a soft mineral, with a hardness of about 2 on the Mohs scale. It is opaque or at most translucent in very thin fragments. Its density is approximately 3.28 g/cm³. ## Colors and Varieties Fervanite occurs in characteristic shades of yellow and brown. The most common colors are golden-yellow, canary-yellow, yellowish-brown, and brown. No named varieties are distinguished. ## History and Name The name fervanite comes from its chemical composition – the Latin words *ferrum* (iron) and *vanadium* (vanadium). The mineral was first described in 1931 by Frank L. Hess and Waldemar T. Schaller based on specimens found in Jurassic deposits on the Colorado Plateau in the USA (Colorado and Utah states). ## Uses Fervanite has no industrial significance. It is solely an object of interest for collectors of rare minerals and scientists.

Properties

Mohs hardness: 2
Luster: Pearly
Streak: Yellow-brown
Density: 3.28
Cleavage: Perfect on {010}
Fracture: Uneven
Transparency: Translucent
Crystal system: Monoclinic

Diagnostic features

## Identification Fervanite can be identified by its characteristic golden-yellow to brown color, fibrous or felted habit, and silky luster. It is very soft and often forms coatings and crusts on host rocks, mainly sandstones. Its occurrence in the oxidation zones of uranium-vanadium deposits is also an important clue. ## Distinguishing from Similar Minerals Fervanite is sometimes confused with other secondary vanadium minerals, such as carnotite or tyuyamunite, which often co-occur with it. However, carnotite has a much more intense, bright yellow color and is strongly radioactive. Hewettite, another vanadate, has a similar habit but usually a darker, deep reddish-brown color. Pascoite is distinguished by its orange-red color and tendency to form crusts. ## Crystal Forms Fervanite crystals are elongated, acicular or bladed, but rarely observed as distinct individuals. They typically form dense, matted or felted masses, as well as radial and fibrous aggregates. Sometimes they occur as small rosettes or spherical clusters (spherulites).

Geological environment

## Genesis Fervanite is a secondary mineral, forming in the oxidation zones of uranium and vanadium ore deposits. It forms as a result of the weathering of primary vanadium minerals, mainly montroseite, in sedimentary rocks such as sandstones and siltstones. Its formation is associated with groundwater activity in arid climates. ## Mineral Associations This mineral often co-occurs with other secondary uranium and vanadium minerals. The most common associations include: hewettite, pascoite, carnotite, tyuyamunite, steigerite, as well as gypsum and selenite. ## Localities The most important and classic localities for fervanite are on the Colorado Plateau in the United States, particularly in Montrose County (Colorado) and Emery and Grand Counties (Utah). It is also known from mines in Apache County, Arizona. Outside the USA, its occurrences have been reported in Gabon (Mounana mine) and Argentina (Mendoza province).

Rarity

Rare

For collectors

## Quality Criteria The most valued specimens by collectors are those with well-formed, radial aggregates of intense, golden-yellow color. A clear contrast with the dark host rock (matrix) enhances its attractiveness. The size and richness of fervanite clusters on the specimen are also important. Due to its delicacy, undamaged specimens, without abrasions and with preserved silky luster, are much more highly valued. ## Popular Localities Classic and most desirable specimens come from historical mines on the Colorado Plateau in the USA, especially from the Paradox Valley area in Colorado and the vicinity of Temple Mountain in Utah. Specimens from these localities are considered type material for this mineral species.

Care and storage

## Cleaning Fervanite specimens are very delicate and brittle. They should be cleaned only with a soft brush or very carefully, using compressed air from a safe distance. Any contact with water or other liquids is inadvisable, as the mineral is soluble in acids and can be damaged. ## What to Avoid Avoid ultrasonic cleaners, all chemical agents (especially acids), and exposure to moisture and water. Due to its low hardness, it must be protected from scratching by harder minerals. Sudden temperature changes should also be avoided. ## Storage It is recommended to store specimens in closed, dry containers or display cases, away from dust and direct sunlight. It is best to place it in a separate box with soft padding to prevent mechanical damage and contact with other minerals.

Sources

IMA Mineral List (CNMNC)