Calcioburbankite

Chemical formula: Na<sub>3</sub>(Ca,Ce<sup>3+</sup>,Sr,La)<sub>3</sub>(CO<sub>3</sub>)<sub>5</sub>

A rare sodium and calcium carbonate from the burbankite group, forming prismatic crystals with a vitreous or greasy luster.

## Characteristics Calcioburbankite is a carbonate mineral belonging to the burbankite group. It is a hydrated carbonate of sodium, calcium, and rare earth elements. It typically forms hexagonal, prismatic crystals, which can be elongated and terminated by pyramids. Crystals often occur as radial or fibrous aggregates. Specimens are usually small, rarely exceeding a few millimeters in length. ## Physical Properties The mineral has a hardness of about 3.5-4 on the Mohs scale and a density of 3.28 g/cm³. It exhibits a vitreous to greasy luster on crystal faces, and a dull luster on fractures. It is brittle and shows poor cleavage. ## Colors and Varieties Calcioburbankite occurs in various colors, most commonly colorless, white, gray, pale yellow, greenish, or pinkish. Its color depends on the rare earth element impurities. No named varieties are distinguished. ## History and Name The mineral's name refers to its chemical composition – the dominance of calcium (Latin: *calx* – lime) and its structural similarity to burbankite. It was first described in 1992 based on material from the Khibiny Massif on the Kola Peninsula in Russia. ## Uses Calcioburbankite has no industrial applications. It is solely an object of interest for collectors specializing in rare minerals and alkaline pegmatite minerals.

Properties

Mohs hardness
3.5-4
Luster
Vitreous, Greasy
Streak
White
Density
3.28
Cleavage
Poor/Indistinct on {1010}
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Hexagonal

Diagnostic features

## Identification A characteristic feature of calcioburbankite is its crystal habit – hexagonal, elongated prisms, often in radial aggregates. Crucial for identification is its vigorous reaction with cold hydrochloric acid. Luster, relatively low hardness, and occurrence in a specific geological environment (alkaline pegmatites) are also important clues. ## Distinguishing from Similar Minerals Calcioburbankite can be confused with other carbonates from the burbankite group, such as burbankite or khanneshite. Distinguishing them requires advanced chemical analyses (EDS/WDS) to determine the dominant cations. Visually, it may resemble some zeolites or scapolite, but it differs from them by its lower hardness and vigorous reaction with acids. ## Crystal Forms It forms well-developed, hexagonal crystals with a prismatic habit, often terminated by pyramid faces. Crystals can be acicular or needle-like and often form radial, stellate, or fibrous aggregates. Less commonly, it occurs as granular masses.

Geological environment

## Genesis Calcioburbankite is a hydrothermal mineral associated with alkaline rocks. It forms in the late stages of crystallization in carbonatites and in nepheline syenite pegmatites, where it crystallizes from solutions rich in sodium, calcium, carbonates, and rare earth elements. ## Mineral Associations This mineral often co-occurs with other rare alkaline minerals. Its typical associations include: eudialyte, lorenzenite, lamprophyllite, microcline, nepheline, aegirine, natrolite, as well as other carbonates like ancylite, synchysite, or burbankite. ## Localities The most important and classic localities for calcioburbankite are in Russia, in the alkaline massifs of the Kola Peninsula (Khibiny and Lovozero). It is also known from the Ilímaussaq complex in Greenland and from Mont Saint-Hilaire in Quebec, Canada. All these places are famous for the occurrence of unique and rare alkaline minerals.

Rarity

Rare

For collectors

## Quality Criteria The most prized specimens by collectors are those with well-formed, sharp, and transparent crystals of intense color (e.g., yellow or pink). Aesthetic radial aggregates are also highly valued, especially when they contrast with matrix minerals such as aegirine or eudialyte. Crystal size is crucial – specimens with crystals exceeding a few millimeters are considered exceptional. ## Popular Localities By far the most sought-after specimens come from the Khibiny and Lovozero massifs on the Kola Peninsula in Russia. Material from Mont Saint-Hilaire in Canada is also valued, often due to the abundance of associated minerals. Specimens from Greenland are less commonly found on the collector's market.

Care and storage

## Cleaning Calcioburbankite specimens should be cleaned very carefully, using a soft brush to remove dust. Brief rinsing in distilled water is permissible, followed by thorough drying. Due to its reactivity with acids, all chemical cleaning agents should be avoided. ## What to Avoid The mineral is sensitive to acids, in which it reacts vigorously, releasing carbon dioxide. Contact with household and laboratory chemicals should be avoided. It should not be heated or exposed to sudden temperature changes. ## Storage Collectible calcioburbankite specimens are best stored under stable conditions, in sealed boxes or display cases, to protect them from dust and mechanical damage. Due to its brittleness, it should be avoided placing it in direct contact with harder minerals.

Sources

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