Alpeite

Chemical formula: Ca<sub>4</sub>Mn<sup>3+</sup><sub>2</sub>Al<sub>2</sub>(Mn<sup>3+</sup>Mg)(SiO<sub>4</sub>)<sub>2</sub>(Si<sub>3</sub>O<sub>10</sub>)(V<sup>5+</sup>O<sub>4</sub>)(OH)<sub>6</sub>

An extremely rare silicate, found as small, dark red crystals in metamorphic manganese deposits.

## Characteristics Alpeite is a complex silicate of calcium, manganese, aluminum, and magnesium, belonging to the group of rare minerals. It occurs as very small, submillimeter crystals with a platy or prismatic habit. These crystals typically form dense, rosette-like aggregates or crusty coatings on the host rock. Due to the small size of the crystals, its macroscopic features are difficult to observe, and full identification requires advanced analytical techniques. ## Physical Properties This mineral has a hardness of approximately 5 on the Mohs scale. It has a vitreous luster, transitioning to resinous. It is translucent, and in thicker aggregates, opaque. Its calculated density is about 3.8 g/cm³. ## Colors and Varieties Alpeite has a characteristic dark red to reddish-brown color. No color varieties or commercial varieties are known. ## History and Name The mineral's name comes from its type locality - the Alps. It was approved as a new mineral species by the International Mineralogical Association (IMA) in 2016. It was discovered and described by a team of mineralogists, including Marco E. Ciriotti, at the Fianel mine in Italy, which is its type locality. ## Applications Due to its extreme rarity and occurrence as microscopic crystals, alpeite has no practical applications. It is solely an object of scientific interest and a prized acquisition for specialized collectors of rare minerals.

Properties

Mohs hardness
5
Luster
Vitreous, Resinous
Streak
Red-brown
Density
3.8
Cleavage
Good on {010}
Fracture
Uneven
Transparency
Translucent to Opaque
Crystal system
Monoclinic

Diagnostic features

## Identification Field identification of alpeite is impossible. Its recognition is based on its characteristic dark red color, occurrence as fine aggregates, and specific geological environment (metamorphosed manganese deposits). Definitive identification requires advanced laboratory methods, such as electron microscopy (EDS) and X-ray diffraction (XRD). ## Differentiation from Similar Minerals Alpeite can be confused with other red or reddish-brown manganese minerals occurring in the same environment, such as piemontite, ganophyllite, or some garnets. Differentiation based on visual characteristics is unfeasible and requires chemical and structural analysis. ## Crystal Forms It forms submillimeter, platy or short-prismatic crystals, most often occurring as radial or rosette-like aggregates and crusts.

Geological environment

## Genesis Alpeite is a mineral of metamorphic origin. It forms in quartz veins cutting braunite-rich rocks within metamorphosed manganese deposits. ## Mineral Associations It most commonly co-occurs with quartz, braunite, ganophyllite, axinite-(Mn), tiragalloite, and saneroite. ## Localities This is an extremely rare mineral, known from only a few localities worldwide. The type locality is the Fianel mine, Canavese, Piedmont, Italy. Its occurrence has also been confirmed at the Cerchiara mine in Liguria, also in Italy.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of collectible alpeite specimens is primarily assessed based on the richness and saturation of crystalline aggregates on the rock matrix. Specimens where microcrystals, despite their small size, are well-formed and create aesthetic clusters are more highly valued. The presence of other rare associated minerals, especially from the type locality, significantly increases the value of the specimen. ## Popular Localities The most sought-after specimens by collectors come from the type locality - the Fianel mine in Italy. This is a historical and classic locality for many rare manganese minerals.

Care and storage

## Cleaning Alpeite specimens, typically micromounts, should be cleaned with the utmost care. For dust removal, it is best to use a soft brush or a photographic air blower. Avoid contact with water and any chemicals. ## What to Avoid The mineral is sensitive to acids. Ultrasonic cleaners should be strictly avoided, as they can damage delicate crystals and their aggregates. Store away from heat sources and protect from sudden temperature changes. ## Storage The safest way to store alpeite specimens is in a specialized micromount box, which protects against dust, shocks, and mechanical damage. Avoid exposure to direct sunlight.

External references

Sources

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