Manganiandrosite-(Ce)

Chemical formula: Mn₂+Ce₃+AlMn₃+Mn₂+(Si₂O₇)(SiO₄)O(OH)

Manganiandrosite-(Ce) is a very rare mineral from the epidote group, distinguished by its complex chemical composition with manganese and cerium.

## Characteristics Manganiandrosite-(Ce) is a complex silicate belonging to the epidote group. It forms prismatic, elongated crystals, up to 2 mm long, which often occur in radial or randomly oriented aggregates. It is a dark mineral, ranging in color from reddish-brown to almost black. ## Physical Properties Crystals exhibit strong pleochroism in shades from dark reddish-brown to yellowish-brown. The mineral is characterized by a vitreous luster. Its Mohs hardness is approximately 6, and its density is high, measured at 4.33 g/cm³. ## History and Name The mineral's name refers to its chemical composition – the dominance of manganese (Mangani-) and its structural similarity to androsite. The suffix -(Ce) indicates cerium as the dominant rare earth element in its structure. It was approved as a new mineral species by IMA in 2011 (IMA2011-039).

Properties

Mohs hardness: 6
Luster: Vitreous
Streak: Brown
Density: 4.33
Cleavage: Good on {001}
Fracture: Uneven
Transparency: Translucent to opaque
Crystal system: Monoclinic

Diagnostic features

## Identification Identification is almost exclusively possible using advanced analytical methods, such as Raman spectroscopy or chemical analysis (EDS/WDS). The dark, reddish-brown color, high density, and co-occurrence with other manganese minerals in a specific geological environment are indicative features. ## Differentiation from Similar Minerals It can be confused with other dark minerals from the epidote group, such as piemontite or androsite-(La). Definitive differentiation requires chemical analysis to determine the dominant rare earth element (cerium) and the precise proportions of manganese at different positions in the crystal structure. ## Crystal Forms It forms columnar or prismatic crystals, usually small in size (up to 2 mm). They occur as radial or disordered aggregates, growing on the surface of the host rock.

Geological environment

## Genesis This is a mineral of metamorphic origin. It forms under low-temperature conditions in manganese-rich rocks that have undergone metasomatism. It occurs in fractures and small veins cutting through these rocks. ## Mineral Associations It co-occurs with minerals such as quartz, albite, tephroite, rhodonite, pyroxmangite, ganophyllite, aegirine, and other manganese minerals. ## Localities The only confirmed locality for this mineral in the world (type locality) is the Cerchiara mine in Liguria, Italy. It is a small, inactive manganese mine known for the occurrence of many rare minerals.

Rarity

Extremely rare

For collectors

## Quality Criteria Due to its extreme rarity, every analytically confirmed specimen is extremely valuable. Microcrystals with a distinct prismatic form, good luster, and intense color, embedded on a contrasting rock matrix, are most highly prized. The size of aggregates and the abundance of occurrence on a given rock fragment also increase the specimen's value.

Care and storage

## Cleaning Due to its extreme rarity and small crystal size, mechanical cleaning is not recommended. If absolutely necessary, compressed air can be used to remove dust. Avoid contact with water and chemicals. ## What to Avoid Avoid ultrasonics, steam cleaners, acids, and all chemical solvents. The mineral should be protected from high temperatures and sudden temperature changes. Due to the small size of the crystals, it is very susceptible to mechanical damage. ## Storage Specimens should be stored exclusively in specialized "micromount" boxes, protecting them from dust, moisture, and physical damage. Storage under stable room conditions is crucial for preserving the integrity of the specimen.

Sources

IMA Mineral List (CNMNC)