Nickenichite

Chemical formula: Na(Ca<sub>0.5</sub>Cu<sup>2+</sup><sub>0.5</sub>)MgMg<sub>2</sub>(As<sup>5+</sup>O<sub>4</sub>)<sub>3</sub>

An extremely rare arsenate of the alluaudite group, forming light blue, granular aggregates in volcanic xenoliths.

## Characteristics Nickenichite is a very rare mineral from the arsenate class, belonging to the alluaudite supergroup. It occurs as very small, granular aggregates or tiny, prismatic crystals, whose size rarely exceeds fractions of a millimeter. Its most characteristic visual feature is its light blue color. ## Physical Properties This mineral is transparent and exhibits a vitreous luster. Its Mohs hardness has not yet been determined. The density calculated based on the chemical formula and unit cell parameters is 3.96 g/cm³. ## Colors and Varieties Nickenichite occurs exclusively in a uniform, light blue color. No color varieties or commercial names are known. ## History and Name The mineral was formally described in 1994. Its name comes from the locality Nickenich in the Eifel mountains in Germany, where this mineral was first identified in volcanic rocks. Interestingly, the material used for the official description and determination of the type characteristics (type material) came from the Inagli Massif in Russia. ## Uses Due to its extreme rarity and occurrence in microscopic quantities, nickenichite has no industrial application. It is solely an object of scientific interest and is valued by specialized collectors of rare minerals.

Properties

Luster
Vitreous
Streak
Light blue
Density
3.96 (obliczona)
Transparency
Transparent
Crystal system
Trigonal

Diagnostic features

## Identification Identification of nickenichite is based on its characteristic light blue color, vitreous luster, and specific occurrence environment. It usually forms very small aggregates, visible only under magnification. Analysis of associated minerals and geological context is crucial. ## Distinguishing from Similar Minerals Nickenichite can be confused with other blue arsenates or members of the alluaudite group, such as johillerite. Definitive differentiation is almost exclusively possible using advanced analytical methods, such as X-ray diffraction (XRD) or chemical microanalysis (EDS). ## Crystal Forms It forms very small, columnar or prismatic crystals, which most often occur as dense, granular aggregates and clusters.

Geological environment

## Genesis Nickenichite forms in two distinct geological environments. In the type locality in Germany, it is a product of fumarolic processes in sedimentary rock xenoliths, entrained by basaltic lavas. In Russia, however, it occurs in strongly metasomatized dolomitic marbles. ## Mineral Associations In Germany (Eifel), it co-occurs with other arsenates of the alluaudite group, johillerite, magnesioferrite, hematite, and diopside. In Russia (Inagli Massif), it is accompanied by turkestanite, kosmochlor, sharyginite, and djerfisherite. ## Localities This is a mineral with extremely limited occurrence, known from only two confirmed locations worldwide: - Nickenicher Sattel near Nickenich, Eifel, Rhineland-Palatinate, Germany (discovery locality). - Inagli Massif, Aldan Shield, Sakha Republic (Yakutia), Russia (type locality).

Rarity

Extremely rare

For collectors

## Quality Criteria Due to its exceptional rarity, any specimen with confirmed nickenichite is valuable. The most highly rated samples are those where the mineral forms rich, clearly visible aggregates under the microscope with an intense blue color. The presence of well-formed crystals of associated minerals is an additional advantage. ## Popular Localities Both known localities - Nickenich in Germany and the Inagli Massif in Russia - are sources of collector specimens, although material from both places is extremely difficult to obtain and appears on the market sporadically, mainly in specialized circulation.

Care and storage

## Cleaning Nickenichite specimens, due to their microscopic size and rarity, should be cleaned dry only, using a soft brush to remove dust. Avoid contact with water, ultrasonic cleaners, and any chemical agents. ## What to Avoid The mineral is an arsenate, so avoid situations that lead to dust formation (e.g., scratching, grinding) and its inhalation or ingestion. After each contact with the specimen, it is recommended to wash your hands. Protect it from mechanical damage, high temperatures, and humidity. ## Storage The safest way to store it is to place the specimen in a sealed "micromount" box, which protects it from dust, light, and mechanical damage. Precise labeling, including location and associated minerals, is important.

Sources

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