Manganokukisvumite

Chemical formula: Na₆Mn₂+Ti₄+₄Si₈O₂₈·₄H₂O

A rare silicate from the kukisvumite group, characterized by brownish, tabular crystals and occurrence in alkaline massifs.

## Characteristics Manganokukisvumite is a rare mineral belonging to the kukisvumite group. It forms tabular or lamellar crystals, often gathered into radial or chaotic aggregates. Its appearance is rather inconspicuous, and individual crystals rarely exceed 1 mm in length. It usually occurs as inclusions in other minerals. ## Physical Properties The mineral is characterized by a vitreous luster. It is brittle and has an uneven fracture. Due to the small size of the crystals, precise determination of physical properties, such as hardness, is difficult. ## Colors and Varieties The typical color of manganokukisvumite is brown in various shades, from light brown to reddish-brown. No color varieties or commercial varieties are known. ## History and Name The mineral's name refers to its chemical composition – the dominance of manganese (mangano) – and its relation to its structural analog, kukisvumite. It was approved as a new mineral by the International Mineralogical Association (IMA) in 2003. It was described by Russian mineralogists from the Kola Peninsula. ## Uses Manganokukisvumite has no industrial application. Its significance is purely scientific and for collectors, as a rare and specific component of agpaitic pegmatites.

Properties

Mohs hardness: 3
Luster: Vitreous
Streak: Light brown
Density: 2.96
Cleavage: Perfect on {001}
Fracture: Uneven
Transparency: Translucent to opaque
Crystal system: Orthorhombic

Diagnostic features

## Identification Identification of manganokukisvumite under amateur conditions is practically impossible. It requires advanced analytical methods, such as chemical analysis (EDS/WDS) and X-ray powder diffraction (XRD). A brownish color, tabular habit, and occurrence in a specific geological environment (agpaitic pegmatites) can be indicative. ## Distinguishing from Similar Minerals It can be confused with other brown titanosilicate minerals found in the same environment, such as lorenzenite, astrophyllite, or lamprophyllite. Differentiation requires specialized studies. Kukisvumite, its close analog, is usually greenish or yellowish, which can be a helpful visual clue. ## Crystal Forms The mineral forms thin, tabular or lamellar crystals, often elongated. These crystals combine into radial, stellate, or randomly arranged aggregates. Single, well-formed crystals are rarely observed.

Geological environment

## Genesis Manganokukisvumite is a mineral of magmatic origin, crystallizing in the late stages of agpaitic pegmatite evolution. It forms in an environment highly saturated with sodium, titanium, and rare earth elements, under conditions of low silica activity. ## Mineral Associations It coexists with a number of other rare alkaline minerals, such as microcline, nepheline, aegirine, eudialyte, lorenzenite, lamprophyllite, lomonosovite, murmanite, villiaumite, and natrosilite. ## Localities The only confirmed and detailed localities of this mineral in the world are in alkaline massifs on the Kola Peninsula in Russia. These are Mount Kukisvumchorr (from which the group name originates) in Khibiny and Mount Alluaiw in the Lovozero massif, where the type specimen was found.

Rarity

Very rare

For collectors

## Quality Criteria The quality of a manganokukisvumite specimen primarily depends on the richness and visibility of the aggregates on the matrix rock. Specimens with distinct, radial clusters of intense, brown color are most valued. Contrast with surrounding minerals (e.g., white nepheline) and the presence of rare associated minerals are also important. ## Popular Localities The only source of collector specimens are two massifs on the Kola Peninsula in Russia: Khibiny and Lovozero. Specimens from Mount Alluaiw (Lovozero) are type material and most sought after by specialized collectors of rare minerals.

Care and storage

## Cleaning Specimens should only be cleaned with compressed air to remove dust. Due to its brittleness and potential reactivity with chemicals, the use of water and any cleaning agents is discouraged. ## What to Avoid Avoid contact with water, acids, and other chemicals. The mineral is brittle, so it should be protected from impacts and vibrations. It should not be heated or subjected to ultrasound. ## Storage It is recommended to store specimens in stable conditions, in closed collector boxes, to protect them from dust, moisture, and mechanical damage. It is best to keep it in its original matrix rock.

Sources

IMA Mineral List (CNMNC)