Calciomurmanite

Chemical formula: (Ca&#₉₇₄₄;)Ti₄+₂(Na&#₉₇₄₄;)Ti₄+₂(Si₂O₇)₂O₂(OH)₂(H₂O)₄

A rare titanium and calcium silicate, closely related to murmanite, distinguished by the dominance of calcium over sodium in specific structural positions.

## Characteristics Calciomurmanite is a rare silicate mineral belonging to the murmanite group. It occurs as thin, tabular or bladed crystals, often forming radial or fan-shaped aggregates. Its color ranges from violet and pinkish-violet to brownish. It is a translucent mineral with a vitreous or pearly luster, particularly noticeable on cleavage surfaces. ## Physical Properties This mineral is characterized by low hardness, approximately 3 on the Mohs scale. It is brittle and possesses perfect cleavage in one direction, causing it to easily split into thin, flexible lamellae. Its density is approximately 2.84 g/cm³. ## Colors and Varieties Calciomurmanite most commonly exhibits shades of violet, from light, pinkish-violet to deeper hues. Brownish and yellowish-brown specimens are also found. No distinct varieties have been identified. ## History and Name The name "calciomurmanite" refers to its chemical composition – the dominance of calcium (Latin: *calcius*) – and its structural and chemical similarity to murmanite. It was officially recognized by the International Mineralogical Association (IMA) in 2004. The type material originates from the Khibiny Massif on the Kola Peninsula in Russia. ## Applications Due to its rarity and small crystal size, calciomurmanite has no industrial applications. It is solely an object of interest for collectors of rare minerals and scientists studying the mineralogy of alkaline rocks.

Properties

Mohs hardness: 3
Luster: Vitreous, Pearly
Streak: White
Density: 2.84
Cleavage: Perfect on {001}
Fracture: Micaceous
Transparency: Translucent
Crystal system: Triclinic

Diagnostic features

## Identification Calciomurmanite can be identified by its characteristic tabular or bladed appearance, violet or brownish color, and perfect cleavage, which causes thin, flexible lamellae to separate. The pearly luster on cleavage surfaces is also a helpful feature. ## Distinguishing from Similar Minerals It can be confused with murmanite, from which it is practically impossible to distinguish without advanced chemical analyses (EDS/WDS) confirming the dominance of calcium over sodium. Other platy minerals, such as micas (e.g., lepidolite), may also have a similar appearance, but calciomurmanite occurs in a very specific geological environment (agpaitic pegmatites). ## Crystal Forms It forms thin, tabular crystals with a rectangular or hexagonal outline. These crystals often combine into packets, fans, or radial aggregates. It rarely occurs as single, well-formed crystals.

Geological environment

## Genesis It is an igneous mineral, crystallizing in the late stages of the evolution of strongly alkaline, silica-undersaturated intrusions (agpaitic rocks). It forms in hydrothermally altered nepheline syenite pegmatites. ## Mineral Associations It most commonly co-occurs with minerals typical of agpaitic pegmatites, such as eudialyte, lorenzenite, nepheline, microcline, aegirine, lamprophyllite, and especially with murmanite, with which it forms intergrowths. ## Localities The most important and best-documented calciomurmanite localities in the world are in Russia, in the ultra-alkaline massifs on the Kola Peninsula. Particularly well-known are localities in the Khibiny Massif (Kirovsky Mine) and the Lovozero Massif (Mount Alluaiv).

Rarity

Very rare

For collectors

## Quality Criteria Specimens with well-formed, sharp crystals of intense, violet color are most valued by collectors. Distinct fan-shaped or radial aggregates, as well as contrasting associations with other rare minerals from the Khibiny and Lovozero massifs, such as brightly colored eudialyte, enhance their attractiveness. Crystal size and absence of mechanical damage are crucial for a specimen's value. ## Popular Localities The vast majority, if not all, collector specimens come from Russia, from two famous alkaline massifs on the Kola Peninsula: Khibiny and Lovozero. Specimens from these localities are considered classic for this mineral.

Care and storage

## Cleaning Specimens should be cleaned very carefully, using a soft brush to remove dust. Due to its low hardness and perfect cleavage, avoid washing in water and any contact with hard tools. Dry cleaning is the safest method. ## What to Avoid Avoid contact with water and chemicals, which can penetrate along cleavage planes and cause the mineral to delaminate. The mineral is brittle and sensitive to mechanical damage, scratches, and impacts. Protect it from sudden temperature changes. ## Storage It is recommended to store specimens in stable conditions, in closed display boxes, away from dust and moisture. Due to its brittleness, it should be isolated from harder minerals to prevent scratching.

Sources

IMA Mineral List (CNMNC)