Vanadoandrosite-(Ce)

Chemical formula: Mn₂+Ce₃+V₃+AlMn₂+O(Si₂O₇)(SiO₄)(OH)

Vanadoandrosite-(Ce) is a very rare mineral from the epidote group, characterized by a complex chemical composition with vanadium, cerium, and manganese.

## Characteristics Vanadoandrosite-(Ce) is a mineral belonging to the allanite subgroup within the epidote group. It forms prismatic crystals up to 1 mm long, which typically occur as radial aggregates or granular masses. It is a darkly colored mineral, with a pitch-black color and a vitreous luster. ## Physical Properties This mineral is characterized by a hardness ranging from 6-7 on the Mohs scale. Its luster is described as vitreous to resinous. It is brittle, and its fracture is uneven to conchoidal. The calculated density is approximately 4.21 g/cm³. ## Colors and Varieties Vanadoandrosite-(Ce) is black, and in thin fragments, it is translucent reddish-brown. No varieties have been distinguished. ## History and Name The mineral's name refers to its chemical composition – the dominance of vanadium (V) and cerium (Ce) – and its relation to an older member of the group, androsite-(La). It was approved as a new mineral by the International Mineralogical Association (IMA) in 2013 (IMA2013-080). It was described by N.V. Chukanov and co-workers. ## Uses Due to its extreme rarity, vanadoandrosite-(Ce) has no industrial applications and is solely an object of scientific interest and a collector's item for specialized collectors of rare minerals.

Properties

Mohs hardness: 6-7
Luster: Vitreous to resinous
Streak: Red-brown
Density: 4.21
Cleavage: Good on {001}
Fracture: Uneven to subconchoidal
Transparency: Translucent in thin splinters, Opaque
Crystal system: Monoclinic

Diagnostic features

## Identification Identifying vanadoandrosite-(Ce) is extremely difficult and impossible without advanced analytical methods, such as electron spectroscopy (EDS/WDS) or X-ray diffraction (XRD). Under collecting conditions, identification relies on a label from a trusted source and knowledge of associated minerals from the type locality. ## Distinguishing from similar minerals This mineral is visually indistinguishable from other black minerals of the epidote group, such as allanite-(Ce), ferriallanite-(Ce), or vanadoallanite-(Ce). The differences lie in subtle proportions of elements (vanadium, iron, aluminum, cerium) at specific positions in the crystal structure, which requires specialized chemical analysis. ## Crystal forms Crystals are prismatic, elongated along the crystallographic b-axis. They typically form radial or stellate aggregates, as well as irregular granular masses within the host rock.

Geological environment

## Genesis Vanadoandrosite-(Ce) forms through hydrothermal or metasomatic processes under specific geochemical conditions, characterized by high concentrations of vanadium, manganese, and rare earth elements (REE), especially cerium. It occurs in veins cutting volcanic rocks. ## Mineral associations This mineral coexists with minerals such as quartz, calcite, hematite, piemontite, aegirine, ardennite-(V), and other minerals from the epidote group. ## Localities The only confirmed occurrence (type locality) of vanadoandrosite-(Ce) is the V-Fe-U-REE polymetallic deposit near Lake Srednyaya, within the Mid-Atlantic Ridge in the Atlantic Ocean.

Rarity

Extremely rare

For collectors

## Quality criteria The quality of a vanadoandrosite-(Ce) specimen is primarily determined by the abundance of the mineral on the rock matrix and the size and development of the crystal aggregates. Due to the microscopic nature of the crystals, even small but well-defined radial clusters are highly prized. Association with other rare minerals is also important. ## Popular localities The only source of specimens is the type locality on the Mid-Atlantic Ridge. Material from this location is extremely difficult to obtain and reaches the collector's market in very limited quantities, usually through scientific institutions or participants of research expeditions.

Care and storage

## Cleaning Specimens should be cleaned very carefully, using only a soft brush to remove dust. Due to its rarity and potential instability, contact with water and any chemical agents should be avoided. ## What to avoid Ultrasonic cleaners, chemical agents (acids, bases, solvents), and sudden temperature changes should be strictly avoided. The mineral is brittle and susceptible to mechanical damage. ## Storage It is recommended to store it under stable conditions, in a closed display box, protecting the specimen from dust, moisture, and direct sunlight. It is best to store it in its original container if purchased as such.

Sources

IMA Mineral List (CNMNC)