Ardennite-(V)

Chemical formula: Mn₂+₄(AlMg)Al₄(Si₅V₅+)O₂₂(OH)₆

Ardennite-(V) is a rare mineral from the silicate group, distinguished by the presence of vanadium and its occurrence in yellowish, radial aggregates.

## Characteristics Ardennite-(V) is a complex sorosilicate mineral from the ardennite group, in which vanadium (V) dominates one of the tetrahedral sites. It typically forms radial or fan-shaped aggregates composed of elongated, bladed crystals. Less common are single, well-formed prismatic crystals. Its appearance is characteristic, and aggregates can reach several centimeters in diameter. ## Physical Properties Crystals exhibit a hardness of 6 on the Mohs scale. They have a vitreous to resinous luster. They are transparent to translucent. The mineral's density is approximately 3.59 g/cm³. ## Colors and Varieties Ardennite-(V) occurs in various shades of yellow, from pale yellow through honey-yellow to yellowish-brown. Pleochroism, a change in color depending on the viewing direction, has also been observed in shades from pale yellow to almost colorless. ## History and Name The mineral's name refers to its relationship with its older, arsenic analogue – ardennite-(As), and to the dominance of vanadium in its chemical composition. It was formally described and approved by the International Mineralogical Association (IMA) in 2012. The type locality is the Valgraveglia mine in Liguria, Italy. ## Uses Due to its rarity and small crystal sizes, ardennite-(V) has no industrial applications. However, it is a valued and sought-after collector's mineral.

Properties

Mohs hardness: 6
Luster: Vitreous
Streak: Pale yellow
Density: 3.59
Cleavage: Good on {010}
Fracture: Uneven
Transparency: Transparent to translucent
Crystal system: Orthorhombic

Diagnostic features

## Identification Key diagnostic features include its yellow color, radial or fan-shaped aggregates of bladed crystals, and specific occurrence environment. The vitreous to resinous luster is also helpful in identification. However, final confirmation requires advanced chemical analysis (EDS) to confirm the presence of vanadium as the dominant element. ## Distinguishing from Similar Minerals Ardennite-(V) can be confused with its arsenic analogue, ardennite-(As), from which it is macroscopically indistinguishable. Other minerals forming yellow, radial aggregates, such as some zeolites or epidotes, may also have a similar appearance. Differentiation requires chemical analysis. ## Crystal Forms It most often forms radial, spherulitic, or fan-shaped aggregates. Crystals are elongated along the [001] axis and flattened, forming bladed habits. Single, prismatic crystals with a rhombic cross-section are less common.

Geological environment

## Genesis Ardennite-(V) is a mineral of metamorphic origin. It forms under low-temperature metamorphic conditions in rocks rich in manganese and silica, such as radiolarites (jaspers). Its crystallization is associated with hydrothermal processes occurring within these rocks. ## Mineral Associations This mineral co-occurs with other manganese minerals and silicates. At the type locality (Valgraveglia, Italy), it was found in association with quartz, braunite, hematite, piemontite, ganophyllite, and cryptomelane. ## Localities Ardennite-(V) is an extremely rare mineral. Besides the type locality in the Valgraveglia mine in Liguria, Italy, its occurrence has been confirmed in the Varenche and St. Marcel mines in the Aosta Valley (Italy) and in Gunma Prefecture, Japan.

Rarity

Very rare

For collectors

## Quality Criteria The most desirable specimens for collectors are those with well-formed, distinct radial or fan-shaped aggregates of intense, honey-yellow color. Samples where ardennite-(V) is well-displayed against a contrasting background of the host rock (matrix), such as dark hematite, are also highly valued. The size of the aggregates and the absence of mechanical damage significantly increase the specimen's value. ## Popular Localities By far the most valued and known specimens come from the type locality – the Valgraveglia mine in Liguria, Italy. Most of the material available on the collector's market originates from there.

Care and storage

## Cleaning Caution is recommended. It is best to use a soft brush to remove dust. If wet cleaning is necessary, use distilled water and avoid prolonged soaking. The specimen should be allowed to dry completely at room temperature. ## What to Avoid Avoid contact with acids and strong detergents, which can damage the mineral's surface. Do not expose it to ultrasonic cleaning or sudden temperature changes. Prolonged exposure to direct sunlight may not be advisable, although there is no detailed data on its photosensitivity. ## Storage Ardennite-(V) specimens are usually small and fragile, so it is best to store them in dedicated collector's boxes, lined with soft material, to prevent mechanical damage. They should be protected from dust and moisture.

Sources

IMA Mineral List (CNMNC)