Calcinaksite

Chemical formula: KNaCa(Si₄O₁₀)·H₂O

Calcinaksite is a rare potassium, sodium, and calcium silicate, forming fibrous aggregates of creamy or beige crystals with a silky luster.

## Characteristics Calcinaksite is a hydrated layered silicate (phyllosilicate) from the group of rare minerals. It occurs as aggregates of elongated, platy, or fibrous crystals, which can form radial or tangled aggregates. Individual crystals are usually small, rarely exceeding a few millimeters in length. The mineral is characterized by a silky luster, especially visible on the surfaces of fibrous aggregates. ## Physical Properties Calcinaksite crystals are relatively soft, with a hardness of about 5 on the Mohs scale. They are brittle and exhibit perfect cleavage in one direction, which is typical for layered silicates. The density of the mineral is approximately 2.59 g/cm³. The luster is vitreous on crystal faces and silky on aggregate surfaces. ## Colors and Varieties Calcinaksite is most often colorless, white, creamy, beige, or pale yellow. No distinct color varieties or commercial varieties are recognized. ## History and Name The mineral's name refers to its chemical composition – the presence of calcium (Calci-), sodium (-na-), and potassium (-k-), and its close structural relationship to the mineral axinite. It was first described in 1993 by N.V. Chukanov and colleagues based on material from the Murun Massif on the Aldan Shield in Russia. ## Uses Calcinaksite has no industrial applications. It is solely an object of interest for collectors specializing in rare minerals and a subject of scientific research.

Properties

Mohs hardness: 5
Luster: Vitreous, Silky
Streak: White
Density: 2.59
Cleavage: Perfect on {100}
Fracture: Uneven
Transparency: Transparent to translucent
Crystal system: Triclinic

Diagnostic features

## Identification Calcinaksite is recognized by its characteristic fibrous or platy aggregates with a silky luster. Its light color (creamy, beige, white) and perfect cleavage in one direction are also important diagnostic features. Occurrence in a specific geological environment (potassium-rich rocks) aids in identification. ## Distinguishing from Similar Minerals Calcinaksite can be confused with other fibrous silicates, such as pectolite, xonotlite, or some zeolites. It differs from pectolite by its lower hardness and different occurrence environment. Final differentiation from very similar minerals, such as tinaksite or charoite (with which it co-occurs), requires advanced analytical methods, such as X-ray diffraction (XRD) or chemical analysis (EDS). ## Crystal Forms The mineral forms elongated, platy crystals, often flattened. They usually occur as radial, tangled, or fibrous aggregates. Single, well-formed crystals are less common.

Geological environment

## Genesis Calcinaksite is a metasomatic mineral. It forms in alkali-rich rocks (especially potassium) that have undergone alteration processes under the influence of hydrothermal solutions. It is typical for fenites, rocks formed at the contact of alkaline intrusions or carbonatites with surrounding silicate rocks. ## Mineral Associations This mineral co-occurs with other rare alkaline minerals. In its type locality (Murun Massif), it is found in association with aegirine, microcline, quartz, tinaksite, charoite, tokkoite, frankamenite, and karnasurtite-(Ce). ## Localities The most important and best-documented occurrence of calcinaksite in the world is its type locality – the Murun Massif on the Aldan Shield, on the border of the Irkutsk Oblast and Yakutia in Russia. This is the only place from which well-characterized specimens of this mineral originate.

Rarity

Very rare

For collectors

## Quality Criteria Specimens with well-formed, radial aggregates exhibiting a distinct silky luster are most valued by collectors. The size and aesthetics of these aggregates are important. A contrasting matrix, e.g., with purple charoite or green aegirine, significantly enhances the visual appeal and value of the specimen. Purity (lack of damage to delicate fibers) is crucial. ## Popular Localities The Murun Massif in Russia is the sole source of collector specimens of calcinaksite. Specimens from this location are the standard for this mineral.

Care and storage

## Cleaning Calcinaksite specimens should be cleaned very carefully, using a soft brush to remove dust. Due to its brittleness and perfect cleavage, mechanical and ultrasonic cleaning should be avoided. If liquid is necessary, brief contact with distilled water is recommended, followed by thorough drying of the specimen. ## What to Avoid Contact with acids and other chemicals that can damage the mineral should be avoided. Calcinaksite is brittle, so it must be protected from impacts, falls, and scratching. It should not be heated or exposed to sudden temperature changes. ## Storage Specimens should be stored in separate, padded collector boxes to prevent mechanical damage and contact with harder minerals. It is best to display them in closed display cases, protecting them from dust and moisture.

Sources

IMA Mineral List (CNMNC)