Naujakasite

Chemical formula: Na₆Fe₂+Al₄Si₈O₂₆

Naujakasite is a rare sodium, iron, and aluminum silicate, forming characteristic, platy crystals with a silvery luster, known primarily from the Ilímaussaq complex in Greenland.

## Characteristics Naujakasite is a complex sodium, iron, and aluminum silicate, belonging to the group of rare minerals. Its most characteristic feature is the formation of platy or scaly aggregates, which rarely form distinct, tabular crystals. Specimens typically have a silvery-white, brownish, or grayish-green color and are distinguished by a strong, almost metallic or pearly luster on cleavage surfaces. ## Physical Properties This mineral is relatively soft, with a Mohs hardness of 2.5-3, meaning it can be scratched by a copper coin. It is quite light, with a density of approximately 2.62 g/cm³. It possesses excellent cleavage in one direction, causing it to easily split into thin, flexible lamellae, similar to micas. The luster is pearly on cleavage planes and vitreous on other surfaces. ## Colors and Varieties Naujakasite occurs in a limited color range. The most common shades are silvery-white, transitioning to brownish, gray, or grayish-green. No named color varieties or commercial varieties are distinguished. ## History and Name The name naujakasite comes from its discovery locality – Naujakasik, in Tunulliarfik Fjord (formerly Tunugdliarfik) in Greenland. The mineral was first described by the Danish mineralogist Ove Balthasar Bøggild in 1933 as part of his research on the mineralogy of the Ilímaussaq alkaline complex. ## Uses Naujakasite has no industrial applications. Its significance is purely scientific and as a collector's item, as a rare and characteristic mineral for the unique geological environment in which it forms.

Properties

Mohs hardness: 2.5-3
Luster: Pearly
Streak: White
Density: 2.615-2.625
Cleavage: Perfect on {001}
Fracture: Uneven
Transparency: Translucent to opaque
Crystal system: Monoclinic

Diagnostic features

## Identification The most important diagnostic feature of naujakasite is its silvery, pearly luster combined with excellent cleavage in one direction, which allows for easy separation of thin, flexible lamellae. Its low hardness (2.5-3) and occurrence in characteristic mineral associations from Greenland are also key. ## Distinguishing from Similar Minerals Naujakasite is sometimes confused with micas (e.g., muscovite, lepidolite) due to similar cleavage and platy appearance. However, it is distinguished by its silvery color, lower transparency of the lamellae, and unique occurrence environment (nepheline syenites). Unlike most micas, it is a monoclinic mineral. ## Crystal Forms Naujakasite crystals are rare and usually take the form of thin, hexagonal tablets. Most often, it forms scaly, platy, or rosette-like aggregates, intergrown in the host rock, mainly in sodalite or lujavrite.

Geological environment

## Genesis Naujakasite is an igneous mineral, crystallizing in the late stages from strongly silica-undersaturated, alkaline magmas. It forms in a specific type of rock – peralkaline nepheline syenites, known as lujavrites, and their pegmatites. ## Mineral Associations This mineral occurs in association with other rare alkaline minerals. Typical associations include sodalite, nepheline, eudialyte, arfvedsonite, steenstrupine-(Ce), aenigmatite, villiaumite, and lorenzenite. It is often intergrown in massive, green sodalite. ## Localities The only significant and confirmed occurrences of naujakasite in the world are within the Ilímaussaq alkaline intrusive complex in southwestern Greenland, particularly in the Tunulliarfik, Kvanefjeld, and Taseq areas. Outside Greenland, its occurrence has been noted in trace amounts in the Khibiny Massif on the Kola Peninsula in Russia.

Rarity

Very rare

For collectors

## Quality Criteria The most valued specimens by collectors are those with well-formed, sharp crystals exhibiting a distinct, silvery luster. Rich aggregates of naujakasite lamellae in a contrasting matrix, especially in intensely green sodalite (hackmanite variety), are also highly prized. Crystal size and absence of mechanical damage significantly increase the value of a specimen. ## Popular Localities By far the best and most classic specimens come from the type locality – the Ilímaussaq complex in Greenland. Material from this location is the standard for the species and practically the only source of specimens available on the collector's market.

Care and storage

## Cleaning Naujakasite specimens should be cleaned very carefully, using a soft brush to remove dust. Due to its excellent cleavage and low hardness, mechanical washing and ultrasonics should be avoided. If liquid is necessary, pure alcohol or distilled water is recommended, applied gently and dried quickly. ## What to Avoid Avoid contact with acids and other chemicals that may react with the mineral. Naujakasite is susceptible to mechanical damage – impacts and scratches can easily cause it to split into lamellae. It should not be heated or exposed to rapid temperature changes. ## Storage It is recommended to store specimens in separate, padded boxes to protect them from scratching and pressure. Due to its platy structure, specimens are fragile and prone to delamination, so they should not be stored loosely with harder minerals.

Sources

IMA Mineral List (CNMNC)