Carbonatecyanotrichite

Chemical formula: Cu₂+₄Al₂CO₃(OH)₁₂·₂H₂O

Carbonatecyanotrichite is a rare secondary mineral of the cyanotrichite group, forming delicate, acicular crystals of an intense blue color.

## Characteristics Carbonatecyanotrichite is a hydrated basic copper and aluminum carbonate, belonging to the cyanotrichite group. It occurs as very small, acicular or hair-like crystals that form radial aggregates, fluffy crusts, and coatings. Individual crystals are usually too small to be seen with the naked eye, and specimens appear as felt-like or velvety masses. ## Physical Properties Carbonatecyanotrichite crystals are extremely delicate and brittle. This mineral is characterized by a silky luster. Its hardness on the Mohs scale is low, estimated at about 2, which, combined with its form of occurrence, makes it very susceptible to mechanical damage. ## Colors and Varieties This mineral is characterized by a distinctive, vivid color, ranging from sky-blue and azure to bluish-green. No color or commercial varieties are distinguished. ## History and Name The mineral's name refers to its chemical composition (presence of a carbonate group) and its structural and visual similarity to cyanotrichite. It was first described in 1964 based on samples from the Grand-Praz mine in Valais, Switzerland. ## Uses Carbonatecyanotrichite has no industrial application. It is solely a mineral of scientific and collectible importance, sought after for its rarity and attractive appearance.

Properties

Mohs hardness: 2
Luster: Silky
Streak: Light blue
Density: 3.17
Cleavage: Perfect on {010}
Fracture: Uneven
Transparency: Translucent
Crystal system: Orthorhombic

Diagnostic features

## Identification Characteristic features include: intense blue color, occurrence in the form of fluffy, felt-like, or radial aggregates composed of microscopic needles, and a silky luster. This mineral often forms crusts on the host rock. It reacts with acids, which is a distinguishing feature from similar sulfates. ## Distinguishing from Similar Minerals It can be confused with cyanotrichite, which is a sulfate and does not react with hydrochloric acid. Aurichalcite may also have a similar appearance, but it usually forms aggregates with a slightly different structure and hue. Final differentiation often requires chemical analysis (EDS) or X-ray diffraction (XRD). ## Crystal Forms Carbonatecyanotrichite forms elongated, acicular or hair-like crystals that combine into radial, star-shaped aggregates, as well as tangled, felt-like or velvety masses and crusts.

Geological environment

## Genesis It is a secondary mineral, formed in the oxidation (weathering) zones of copper ore deposits. It forms as a result of the action of carbonate-rich waters on primary minerals containing copper and aluminum, in an environment with low sulfate content. ## Mineral Associations It co-occurs with other secondary copper and zinc minerals, such as malachite, azurite, brochantite, tyrolite, as well as with quartz, calcite, and limonite. ## Localities Key occurrences of this rare mineral include the Grand-Praz mine in Valais (Switzerland), Cap Garonne (France), Laurion (Greece), the Clara mine in the Black Forest (Germany), and some localities in Arizona (USA).

Rarity

Rare

For collectors

## Quality Criteria The most prized specimens are those with rich, fluffy crusts of intense blue color, covering a significant area of the host rock. Contrast with clear quartz or another rock enhances visual appeal. Due to the microscopic size of the crystals, their individual form is not a criterion for evaluation – the quality and aesthetics of the entire aggregate are what matter. ## Popular Localities Specimens from classic localities such as Cap Garonne in France, Laurion in Greece, or the Clara mine in Germany are particularly sought after by collectors specializing in rare minerals and "micromount" specimens.

Care and storage

## Cleaning Specimens should be cleaned very carefully, using compressed air to remove dust. Any contact with water, especially with brushes, is highly inadvisable and risks irreversible damage to the delicate crystals. ## What to Avoid Contact with water, acids, and other chemicals must be strictly avoided. The mineral is sensitive to ultrasound and vibrations. It should not be heated or exposed to prolonged humidity. ## Storage Carbonatecyanotrichite specimens require storage in closed, stable containers (e.g., "micromount" type) that protect them from dust, humidity, and mechanical damage. Avoid places exposed to vibrations.

Sources

IMA Mineral List (CNMNC)