Manganberzeliite

Chemical formula: NaCa₂Mn₂+₂(As₅+O₄)₃

A rare arsenate of the berzeliite group, forming granular aggregates and small crystals with a characteristic, intense orange to reddish-brown color.

## Characteristics Manganberzeliite is a sodium, calcium, and manganese arsenate belonging to the berzeliite group. It rarely forms distinct, isometric crystals, most often as rhombic dodecahedra. It usually occurs as fine-grained, massive, or compact aggregates, strongly intergrown with the host rock. Its most characteristic feature is its intense, vivid color. ## Physical Properties This mineral is characterized by a hardness in the range of 4.5-5 on the Mohs scale. It has a vitreous to greasy luster. It is a relatively heavy mineral, with a density of approximately 4.2 g/cm³. It is brittle and exhibits an uneven or conchoidal fracture. ## Colors and Varieties Manganberzeliite ranges in color from yellow, through orange, reddish-orange, to reddish-brown. Its color is one of its main diagnostic features. No named varieties are distinguished, and color variability depends on minor impurities and crystallization conditions. ## History and Name The mineral's name, given in 1886 by Georg Flink, refers to its chemical composition – the dominance of manganese – and its structural similarity to berzeliite. The name of the berzeliite group, in turn, honors the Swedish chemist Jöns Jacob Berzelius. ## Uses Due to its rarity and typically small size of occurrences, manganberzeliite has no industrial application. However, it is a valued and sought-after collector's mineral.

Properties

Mohs hardness: 4.5-5
Luster: Vitreous to greasy
Streak: Yellowish-orange
Density: 4.2
Cleavage: None
Fracture: Uneven to conchoidal
Transparency: Translucent to opaque
Crystal system: Cubic

Diagnostic features

## Identification The most important diagnostic features of manganberzeliite are its intense orange to reddish-brown color, vitreous or greasy luster, and occurrence in granular, massive aggregates. Hardness (4.5-5) is also helpful. It reacts with hydrochloric acid. ## Distinguishing from Similar Minerals It can be confused with other manganese arsenates, such as sarkinite or brandtite, which often co-occur with it. Differentiation usually requires chemical or crystallographic analysis. It is distinguished from similarly colored garnets (spessartine) by its lower hardness. ## Crystal Forms Crystals are rare and usually very small, taking the form of rhombic dodecahedra or irregular grains. It is most commonly found as massive, compact, or granular aggregates, filling small fissures and cavities in the rock.

Geological environment

## Genesis This is a mineral of metamorphic origin. It forms as a result of contact or regional metamorphism of manganese and iron ore deposits that have undergone metasomatism. It forms in skarns and other manganese-rich metamorphic rocks. ## Mineral Associations It co-occurs with other manganese minerals, such as hausmannite, braunite, tephroite, rhodonite, as well as with other arsenates, e.g., sarkinite, brandtite, and with barite, calcite, and garnets of the andradite group. ## Localities The most important and classic localities for this mineral are in Sweden, in the Långban and Sjögruvan mines (Värmland region), and in the Franklin mine in New Jersey, USA. It is also known from the Gozaisho mine in Japan and from several places in Switzerland (e.g., Val d'Anniviers).

Rarity

Rare

For collectors

## Quality Criteria The most highly valued specimens are those with well-formed, even if small, crystals of intense, vivid color, set on a contrasting rock matrix. Rich, massive aggregates of bright orange color are also attractive. Clarity is not a key criterion, as the mineral is inherently opaque. ## Popular Localities The most sought-after specimens by collectors come from historical localities in Sweden (Långban) and the Franklin mine in the USA. Material from these sites is considered classic and fetches the highest prices.

Care and storage

## Cleaning Specimens should only be cleaned mechanically, using a soft, dry brush to remove dust. Compressed air may be used. Water, especially with detergents, should be avoided, as the mineral is an arsenate and contact with water can lead to slow chemical reactions. ## What to Avoid Contact with acids and other chemicals that can damage or dissolve the mineral should be strictly avoided. Specimens should not be heated or exposed to prolonged intense sunlight, which theoretically may affect their color. Protect from moisture. ## Storage Store in stable conditions, in a dry place, preferably in a closed display case or cabinet, to protect against dust and mechanical damage. Due to its arsenic content, it is recommended to wash hands after handling the specimen.

Sources

IMA Mineral List (CNMNC)