Manganostibite

Chemical formula: Mn₂+₇Sb₅+As₅+O₁₂

Manganostibite is a rare arsenate mineral, an oxide of manganese, antimony, and arsenic, found in metamorphic deposits.

## Characteristics Manganostibite is a very rare arsenate mineral. It occurs as granular or massive aggregates, rarely forming poorly developed, small crystals. Its structure is similar to manganomanganite. It is an opaque mineral with a black color and metallic luster. ## Physical Properties This mineral is characterized by a hardness of 5 on the Mohs scale. It has a metallic luster and is opaque. Its density is relatively high, approximately 5.19 g/cm³. ## Colors and Varieties Manganostibite is a mineral of uniform, black color. No color or commercial varieties are distinguished. ## History and Name The mineral's name, given in 1884 by Lars Johan Igelström, refers to its chemical composition – the presence of manganese (mangan) and antimony (Latin: stibium). It was discovered in the Sjögruvan mine in Sweden. ## Applications Due to its extreme rarity, manganostibite has no industrial applications. It is solely an object of interest for collectors specializing in rare minerals and for scientific institutions.

Properties

Mohs hardness: 5
Luster: Metallic
Streak: Black
Density: 5.19
Cleavage: None
Fracture: Uneven
Transparency: Opaque
Crystal system: Cubic

Diagnostic features

## Identification Identifying manganostibite under amateur conditions is practically impossible. It requires advanced analytical methods, such as chemical composition analysis (EDS/WDS) and X-ray diffraction (XRD). It can be tentatively suspected in the case of black, metallic aggregates within metamorphic manganese deposits, especially in known localities. ## Distinguishing from Similar Minerals Manganostibite can be confused with many other black, metallic oxide minerals often found in similar environments, such as magnetite, hausmannite, jacobsite, or franklinite. Differentiation without specialized equipment is impossible. ## Crystal Forms This mineral most often forms massive, granular aggregates embedded in rock. Very rarely, small, poorly developed crystals with a regular (octahedral) habit are observed.

Geological environment

## Genesis Manganostibite is a mineral of metamorphic origin. It forms as a result of contact or regional metamorphism of manganese and iron ore deposits. It occurs in rocks such as skarns and metamorphosed Fe-Mn deposits. ## Mineral Associations It co-occurs with other manganese minerals, such as hausmannite, magnetite, tephroite, sonolite, alleghanyite, galaxite, jacobsite, as well as with barite and phlogopite. ## Localities The most important and classic localities for this mineral are in Sweden, in the Värmland region (Sjögruvan and Långban mines) and in Västmanland (Nordmark). It is also known from a small occurrence in Japan (Gozaisho mine, Fukushima Prefecture).

Rarity

Very rare

For collectors

## Quality Criteria The quality of a manganostibite specimen is determined primarily by its quantity and degree of crystallization. Specimens with visible, even if small, crystals are most desirable. Since it is an embedded mineral, the aesthetics of the rock matrix and the richness of associations with other rare minerals are also important. ## Popular Localities By far the most valued and historically important specimens come from the Swedish mines in Långban and Nordmark. These are classic localities from which most of the material available on the collector's market originates.

Care and storage

## Cleaning Manganostibite specimens should only be cleaned mechanically, using a soft brush or compressed air to remove dust. Avoid contact with water and any chemical agents. ## What to Avoid Absolutely avoid contact with water, acids, and other chemicals that may react with the mineral. Do not heat it or subject it to ultrasound. As a mineral containing arsenic, avoid inhaling dust during cleaning or handling. ## Storage It is recommended to store specimens in a dry place, preferably in a sealed container or display box, to protect them from moisture and dust. Avoid exposure to direct sunlight.

Sources

IMA Mineral List (CNMNC)