Manganonaujakasite

Chemical formula: Na₆Mn₂+Al₄Si₈O₂₆

Manganonaujakasite is a very rare sodium, manganese, and aluminum silicate, distinguished by its perfect, platy cleavage and occurrence in the Ilimaussaq alkaline complex in Greenland.

## Characteristics Manganonaujakasite is the manganese analogue of naujakasite, belonging to the silicate group. It forms pale brown, tabular or platy aggregates, often intergrown with other minerals. Its most characteristic visual feature is perfect cleavage in one direction, which causes it to break into thin, mica-like flakes. On cleavage surfaces, it exhibits a strong pearly luster, while on other surfaces, it is vitreous. ## Physical Properties This mineral is relatively soft and very brittle due to its structure. Its density is approximately 2.62 g/cm³. It is transparent to translucent. A key physical property is its perfect, unidirectional cleavage, which gives it a mica-like appearance. ## Colors and Varieties The typical color of manganonaujakasite is pale brown. No named varieties are distinguished, which is understandable for such a rare mineral. ## History and Name The mineral's name refers to its chemical composition – the dominance of manganese – and its close relationship to naujakasite. It was officially recognized as a new mineral species by the International Mineralogical Association (IMA) in 1999. It was described by S. Karup-Møller and O.V. Petersen based on material from the Ilimaussaq alkaline complex in Greenland, which is its type locality. ## Applications Due to its extreme rarity and small size of occurrences, manganonaujakasite has no industrial applications. It is solely an object of interest for specialized collectors of rare minerals and scientists.

Properties

Luster: Pearly, Vitreous
Streak: White
Density: 2.62
Cleavage: Perfect on {001}
Fracture: Uneven
Transparency: Transparent to translucent
Crystal system: Monoclinic

Diagnostic features

## Identification The most important diagnostic feature of manganonaujakasite is its perfect, unidirectional cleavage, which causes it to break into thin flakes with a pearly luster. The pale brown color combined with the occurrence location (alkaline complexes) and specific mineral paragenesis is a strong indicator. However, final confirmation requires advanced chemical analysis. ## Distinguishing from Similar Minerals Manganonaujakasite is visually almost indistinguishable from its analogue, **naujakasite**, which, however, usually has a gray, greenish-gray, or white color. It can also be confused with some **micas** (e.g., biotite, phlogopite), but mica flakes are usually more flexible. A definitive distinction from naujakasite is only possible through chemical analysis (EDS/WDS) to confirm the dominance of manganese over iron. ## Crystal Forms This mineral forms aggregates composed of platy or tabular crystals, often arranged in parallel. Well-formed, single crystals are rarely found. It usually occurs as intergrown clusters within the rock mass.

Geological environment

## Genesis Manganonaujakasite forms in a unique geological environment, namely highly alkaline (peralkaline) igneous rocks, such as nepheline syenites and associated pegmatites. It is a mineral of the late stages of magma crystallization or forms in hydrothermal processes within these rocks, especially in lujavrites. ## Mineral Associations This mineral coexists with a whole range of other rare minerals typical of alkaline complexes. Its most common associations include: naujakasite, arfvedsonite, aegirine, eudialyte, nepheline, sodalite, steenstrupine-(Ce), ussingite, and villiaumite. ## Localities The most important and classic occurrence of manganonaujakasite is its type locality – the Ilimaussaq alkaline complex in southern Greenland, especially the Kvanefjeld and Tupersuatsiait areas. Its presence has also been confirmed in another famous alkaline massif – Lovozero on the Kola Peninsula in Russia.

Rarity

Very rare

For collectors

## Quality Criteria For such a rare mineral, any specimen with confirmed identity is valuable. The most highly valued are rich clusters of platy crystals with a distinct, pale brown color, contrasting with the matrix. Specimens where manganonaujakasite coexists with other rare, well-formed minerals from the given locality, forming aesthetic parageneses, are particularly desirable. ## Popular Localities Practically all manganonaujakasite specimens available on the collector's market come from one place in the world: the Ilimaussaq complex in Greenland. This is the source of the best and largest known clusters of this mineral.

Care and storage

## Cleaning The mineral is extremely delicate due to its perfect cleavage. It should only be cleaned dry, using a very soft brush to remove dust. Contact with water, especially tap water, is not recommended. As a last resort, distilled water can be used, applied in minimal amounts, and the specimen immediately dried. ## What to Avoid Avoid any mechanical stress, impacts, falls, and vibrations (including ultrasonic cleaners), which can cause the specimen to break into small flakes. The mineral is soft, so it must be protected from scratching by harder minerals. Avoid contact with acids and other chemicals. ## Storage Manganonaujakasite specimens are best stored in separate, padded "membrane boxes" or in containers with soft lining, away from other minerals. It is not suitable for display without proper protection.

Sources

IMA Mineral List (CNMNC)