Parsettensite

Chemical formula: (K,Na,Ca)<sub>7.5</sub>(Mn<sup>2+</sup>,Mg)<sub>49</sub>Si<sub>72</sub>O<sub>168</sub>(OH)<sub>50</sub>·nH<sub>2</sub>O

Parsettensite is a rare, brown, fibrous silicate mineral found in manganese deposits in the Swiss Alps.

## Characteristics Parsettensite is a complex manganese, potassium, sodium, and calcium silicate, belonging to the stilpnomelane group. It forms characteristic radial or tangled aggregates with a fibrous structure, less commonly lamellae or scales. Its appearance is quite distinctive, often resembling asbestos or mineral wool aggregates, with a silky luster on the fiber surfaces. ## Physical Properties This mineral is relatively soft, with a Mohs hardness of approximately 4. It has a silky luster, and a dull or earthy luster on fracture surfaces. It is opaque. The density of parsettensite ranges from 2.61-2.63 g/cm³. ## Colors and Varieties Parsettensite occurs in shades of brown – from light brown and brownish-yellow to dark brown, and even brownish-black. No named varieties are distinguished. ## History and Name The mineral's name comes from its discovery locality – Piz da la Parsettens peak in the canton of Graubünden, Switzerland. It was first described in 1925 by the Swiss mineralogist Walter Frederick Epprecht. ## Uses Parsettensite has no industrial applications. It is solely an object of interest for collectors specializing in rare or systematic minerals.

Properties

Mohs hardness
4
Luster
Silky
Streak
Light brown
Density
2.61-2.63
Cleavage
Perfect on {001}
Fracture
Uneven
Transparency
Opaque
Crystal system
Monoclinic

Diagnostic features

## Identification Parsettensite can be identified by its characteristic fibrous or radial aggregate forms, as well as its brown color and silky luster. It is soft and often forms aggregates resembling felted mineral wool. Its occurrence in association with other manganese minerals in metamorphic rocks is a strong indicator. ## Distinguishing from Similar Minerals It can be confused with other fibrous manganese or iron minerals, such as stilpnomelane or pyroxmangite. Stilpnomelane is usually darker (almost black) and forms more platy aggregates. Other manganese silicates often have different crystal forms or higher hardness. ## Crystal Forms Parsettensite does not form well-developed, single crystals. It occurs as fibrous aggregates, often radial, tangled, or spherulitic. It is also found in the form of platy, scaly, or rosette aggregates.

Geological environment

## Genesis It is a low-temperature hydrothermal mineral, formed as a result of the metamorphism of sedimentary manganese deposits. It forms in fractures and veins cutting through manganese-rich rocks, such as radiolarites or jaspers. ## Mineral Associations Parsettensite often co-occurs with other manganese minerals. Its typical associated minerals include: braunite, rhodochrosite, pyroxmangite, rhodonite, aegirine, quartz, and barite. ## Localities The most important and classic parsettensite localities are in the Alps, in the canton of Graubünden, Switzerland, particularly in the Oberhalbstein region (e.g., Falotta, Piz da la Parsettens). It also occurs in Italy in the Aosta Valley (Praborna mine) and in the Liguria region. It is also known from several localities in Japan (e.g., Noda-Tamagawa mine).

Rarity

Rare

For collectors

## Quality Criteria The most valued specimens by collectors are those with well-defined, radial fibrous aggregates exhibiting an intense, silky luster. Contrast with a light matrix rock (e.g., white quartz) significantly enhances the visual appeal of the specimen. Large, undamaged rosettes or spherulites are rare and sought after. ## Popular Localities Classic and most desirable specimens come from the Swiss Alps, from localities in Graubünden. Specimens from the Praborna mine in Italy are also highly prized in collections.

Care and storage

## Cleaning Parsettensite specimens are very delicate and brittle. They should only be cleaned with a soft brush or very carefully, using compressed air from a safe distance. Avoid contact with water, which can penetrate the fibrous structure and weaken the aggregate. ## What to Avoid Ultrasonic cleaners, all chemical agents, acids, and detergents should be strictly avoided. The mineral is sensitive to shocks and impacts, which can cause it to disintegrate. It should be protected from moisture. ## Storage It is recommended to store specimens in closed, padded collector boxes to protect them from dust, mechanical damage, and moisture. Due to its fibrous structure, direct handling should be avoided to prevent crumbling and spreading of fine fibers.

Sources

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