Cerchiaraite-(Mn)

Chemical formula: Ba<sub>4</sub>Mn<sup>3+</sup><sub>4</sub>(Si<sub>4</sub>O<sub>12</sub>)O<sub>2</sub>(OH)<sub>4</sub>Cl<sub>2</sub>[Si<sub>2</sub>O<sub>3</sub>(OH)<sub>4</sub>]

A rare mineral from the cerchiaraite group, characterized by its unique chemical composition and intensely blue crystal color.

## Characteristics Cerchiaraite-(Mn) is a very rare silicate mineral belonging to the cerchiaraite group. It forms elongated, prismatic crystals with a square cross-section, reaching up to 2 mm in length. It typically occurs as radial or tangled aggregates. Its most characteristic feature is its intense, azure-blue or dark blue color. ## Physical Properties This mineral is characterized by a vitreous luster and is transparent to translucent. Its Mohs hardness is approximately 4.5, and its density ranges between 3.75 and 3.81 g/cm³. It is brittle and exhibits an uneven fracture. ## Colors and Varieties Cerchiaraite-(Mn) occurs in shades from azure-blue to dark blue. No distinct varieties have been identified. ## History and Name The mineral's name refers to its type locality – the Cerchiara mine in Italy – and to the manganese (Mn) dominant in its composition. It was approved as a new mineral species by the International Mineralogical Association (IMA) in 2013. Its discovery and description are the result of research by a team of mineralogists, including G. Della Ventura and F. Bellatreccia. ## Uses Due to its extreme rarity, cerchiaraite-(Mn) is solely an object of scientific and collector interest. It has no industrial applications.

Properties

Mohs hardness
4.5
Luster
Vitreous
Streak
Light blue
Density
3.75 - 3.81
Cleavage
Imperfect on {100} and {010}
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Tetragonal

Diagnostic features

## Identification Cerchiaraite-(Mn) can be identified by its characteristic, intense blue color, prismatic crystal habit, and specific occurrence environment. Vitreous luster and relatively low hardness are also helpful indicators. ## Distinguishing from Similar Minerals It can be confused with other blue minerals from metamorphic environments, such as linarite, azurite, or lazurite. However, it is distinguished by its crystal habit (elongated prisms), specific mineral associations (e.g., with aegirine, sugilite), and lower hardness compared to lazurite. Final confirmation requires advanced chemical (EDS) or X-ray (XRD) analyses. ## Crystal Forms It forms elongated, acicular, or prismatic crystals with a square cross-section. Crystals often form radial, stellate, or haphazardly tangled aggregates embedded in the host rock.

Geological environment

## Genesis It is a hydrothermal mineral, associated with metasomatic processes within metamorphosed sedimentary rocks rich in manganese. It forms in veins cutting through siliceous marbles and schists. ## Mineral Associations It most commonly co-occurs with minerals such as aegirine, quartz, calcite, barite, hematite, sugilite, pyroxmangite, and other rare manganese minerals. ## Localities The most important and well-documented localities worldwide are: - Cerchiara Mine, Liguria, Italy - the type locality, where the best-formed specimens were found. - N’Chwaning II Mine, Northern Cape Province, Republic of South Africa - known for its occurrence in association with sugilite.

Rarity

Very rare

For collectors

## Quality Criteria The most highly valued cerchiaraite-(Mn) specimens are characterized by an intense, deep blue color and well-formed, undamaged crystals. Rich radial aggregates or single, isolated crystals on a contrasting matrix (e.g., on white calcite or quartz) are particularly sought after. The size of the crystals and the entire specimen also significantly influence its value. ## Popular Localities Specimens from the Cerchiara mine in Italy are considered exemplary for this mineral. Material from the N’Chwaning mine in South Africa, although also valued, often has a slightly different habit and occurs in a different mineral environment.

Care and storage

## Cleaning Specimens should be cleaned very carefully, using a soft brush to remove dust. Brief rinsing in distilled water is permissible, followed by thorough drying. Ultrasonic cleaners should be avoided. ## What to Avoid The mineral is sensitive to acids and strong chemicals. It should be protected from sudden temperature changes and prolonged exposure to direct sunlight, which theoretically could affect its color. ## Storage It is recommended to store specimens in stable conditions, in closed display boxes, away from dust and humidity. Due to its brittleness, contact with harder minerals that could scratch or damage it should be avoided.

Sources

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