Demagistrisite

Chemical formula: BaCa₂Mn³⁺₄(Si₃O₁₀)(Si₂O₇)(OH)₄·3H₂O

Demagistryt is a very rare mineral with a complex chemical composition, forming reddish-brown, tabular crystals, discovered in Italy.

## Characteristics Demagistryt is a very rare, hydrated barium, calcium, and manganese silicate. It occurs as small, tabular or platy crystals, reaching up to 1 mm in size. It forms rosette-like or spherulitic aggregates. Its characteristic features include a reddish-brown color and vitreous luster. ## Physical Properties Demagistryt crystals exhibit a hardness of approximately 4 on the Mohs scale. They are brittle, and their density is about 3.43 g/cm³. The luster is described as vitreous, and the mineral is translucent. ## Colors and Varieties This mineral occurs in a uniform, reddish-brown color. No varieties have been distinguished. ## History and Name Demagistryt was discovered in the Cerchiara mine in Liguria, Italy, and approved as a new mineral species by the IMA in 2012. The name honors the Italian mineral collector, Antonio "Toni" de Magistris (1942-2010), for his contribution to mineralogical research in the Ligurian region.

Properties

Mohs hardness
4
Color
orange brown to red brown
Luster
Vitreous
Streak
beige
Density
3.43
Cleavage
Perfect on {001}
Fracture
Irregular/Uneven
Transparency
Transparent,Translucent
Crystal system
Orthorhombic

Diagnostic features

## Identification Characteristic features of demagistryt include its reddish-brown color, tabular crystal habit, vitreous luster, and occurrence in a specific geological environment. Final identification requires advanced analytical methods, such as XRD or EDS, due to its resemblance to other manganese silicates. ## Distinguishing from Similar Minerals It can be confused with other rare manganese minerals from the same locality, such as saneroite or ganophyllite. Distinguishing it with the naked eye is practically impossible and requires specialized analysis. ## Crystal Forms Demagistryt forms thin, tabular crystals with a hexagonal outline, often grouped into rosette-like or spherulitic aggregates.

Geological environment

## Genesis Demagistryt forms as a result of hydrothermal processes in veins cutting through rocks rich in manganese and barium, mainly in radiolarite (jasper) sediments. It is a secondary mineral, crystallizing in fractures and small rock cavities. ## Mineral Associations This mineral co-occurs with other manganese minerals and silicates, such as quartz, braunite, saneroite, ganophyllite, hematite, barite, and calcite. ## Localities The only confirmed occurrence of demagistryt in the world is its type locality – the Cerchiara mine, located in the Val di Vara valley in Liguria, Italy.

Rarity

Extremely rare

For collectors

## Quality Criteria The most prized demagistryt specimens are those with well-formed, sharp crystals forming aesthetic, rosette-like aggregates. Contrast with the surrounding matrix, most often jasper or quartz, is important. Due to the microscopic size of the crystals, specimens are primarily evaluated under magnification. ## Popular Localities All known collector specimens come from a single location in the world: the Cerchiara mine in Italy. This makes the mineral extremely desirable for collectors specializing in rare species and "micromount" type minerals.

Care and storage

## Cleaning Due to its brittleness and rarity, mechanical cleaning is discouraged. If necessary, compressed air can be used to remove dust. Contact with water should be limited due to the mineral's hydrated nature. ## What to Avoid Avoid contact with chemicals, acids, and detergents. The mineral is brittle and sensitive to ultrasound. It should be protected from high temperatures, which can lead to dehydration and structural damage. ## Storage Demagistryt specimens should be stored in stable conditions, in sealed "micromount" boxes, protecting them from mechanical damage, dust, and sudden changes in humidity.

External references

Sources

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