Mangano-ferri-eckermannite

Chemical formula: NaNa₂(Mn₂+₄Fe₃+)Si₈O₂₂(OH)₂

A rare sodium amphibole from the eckermannite group, distinguished by its high manganese and iron content, found in metamorphic deposits.

## Characteristics Mangano-ferri-eckermannite is a mineral belonging to the sodium amphibole group. It is a member of the eckermannite series, in which manganese (Mn²⁺) and ferric iron (Fe³⁺) are the dominant cations. It forms prismatic, fibrous, or bladed crystals, often aggregated. Its color is usually dark, from brown to black, which is typical for iron-rich amphiboles. ## Physical Properties This mineral is characterized by a vitreous luster. Its Mohs hardness is approximately 6, and its density ranges between 3.3 and 3.4 g/cm³. It is an opaque mineral. ## History and Name The name "mangano-ferri-eckermannite" directly refers to its chemical composition – it indicates the dominance of manganese (mangano) and trivalent iron (ferri) and its belonging to the eckermannite subgroup. It was formally described as a new mineral species relatively recently, after detailed chemical and crystallographic studies of specimens from Norway. ## Applications Due to its rarity, mangano-ferri-eckermannite has no industrial applications. It is solely an object of scientific and collecting interest for advanced systematic and rare mineral collectors.

Properties

Mohs hardness: 6
Luster: Vitreous
Streak: Gray
Density: 3.3-3.4
Cleavage: Perfect on {110}
Fracture: Uneven
Transparency: Opaque
Crystal system: Monoclinic

Diagnostic features

## Identification Identification of mangano-ferri-eckermannite is extremely difficult without advanced analytical methods. Preliminary identification is based on its dark color, prismatic habit, and co-occurrence with other manganese minerals. Definitive identification requires chemical analysis (e.g., EDS/WDS) to confirm the dominance of manganese and iron in the appropriate structural positions. ## Distinguishing from similar minerals This mineral is visually indistinguishable from other dark amphiboles, such as arfvedsonite, riebeckite, or other minerals from the eckermannite subgroup. The differences lie in subtle changes in chemical composition, impossible to verify without specialized equipment. ## Crystal forms It most commonly occurs as elongated, prismatic crystals with a bladed or acicular habit. These crystals often form radial or disordered aggregates and clusters.

Geological environment

## Genesis Mangano-ferri-eckermannite forms under conditions of regional metamorphism, in rocks rich in manganese and sodium. Its presence is associated with manganese ore deposits that have been subjected to medium and high pressures and temperatures. ## Mineral associations In its type locality (Nyberget, Norway), it co-occurs with quartz, rhodochrosite, orthoclase, braunite, hematite, and piemontite. The presence of these minerals, especially those rich in manganese, is a key environmental indicator. ## Localities The only confirmed and thoroughly described locality of this mineral worldwide is the Nyberget manganese ore deposit in the Värmland region, Sweden. This is its type locality.

Rarity

Very rare

For collectors

## Quality criteria The quality of a mangano-ferri-eckermannite specimen is primarily assessed based on the richness and development of its crystals. The most desirable specimens are those with clearly visible, well-formed prismatic crystals, forming aesthetic clusters on the rock matrix. Contrast with clear quartz or pink rhodochrosite significantly enhances visual appeal. ## Popular localities The only source of collector specimens is the historical type locality – Nyberget in Sweden. Material from this location is extremely rare on the market.

Care and storage

## Cleaning Specimens should be cleaned mechanically only, using a soft, dry brush or compressed air to remove dust. Avoid contact with water and any chemical agents. ## What to avoid Avoid contact with acids and other chemicals that may react with the mineral. It should not be heated or subjected to ultrasound. Prolonged exposure to moisture can be harmful. ## Storage It is recommended to store in a dry place, in a closed display box or cabinet, away from dust and direct sunlight. Due to possible fragility, it should be protected from impacts.

Sources

IMA Mineral List (CNMNC)