Schneiderhöhnite

Chemical formula: Fe²⁺Fe³⁺₃As³⁺₅O₁₃

A rare iron arsenite with a characteristic black color and excellent cleavage, found mainly in the Tsumeb mine in Namibia.

## Characteristics Schneiderhöhnite is a complex iron(II) and iron(III) arsenite. It forms tabular or lamellar crystals, often gathered into radial or chaotic aggregates. Typical specimens have a black or blackish-brown color and are opaque or only translucent on thin edges. The luster can be metallic to submetallic. ## Physical Properties This mineral is relatively soft, with a Mohs hardness of 3. Its density is approximately 4.3 g/cm³, which is a significant value for a non-metallic mineral. It exhibits perfect cleavage in one plane, causing it to easily split into thin flakes, and its fracture is described as micaceous. ## Colors and Varieties Schneiderhöhnite usually occurs in a uniform, black to blackish-brown color. No color varieties or commercial varieties are distinguished. ## History and Name The mineral was first described in 1973 based on specimens found in the famous Tsumeb mine in Namibia. Its name honors Hans Schneiderhöhn (1887-1962), a German geologist and mineralogist who was an expert in ore deposits, including the Tsumeb deposit. ## Uses Schneiderhöhnite has no industrial application. It is solely a mineral of scientific and collector's interest.

Properties

Mohs hardness: 3
Luster: Metallic to submetallic
Streak: Brown
Density: 4.3
Cleavage: {100} perfect; two others distinct.
Fracture: Micaceous
Transparency: Translucent
Crystal system: Triclinic

Diagnostic features

## Identification Schneiderhöhnite can be identified by its black color, metallic or submetallic luster, relatively high density, and characteristic perfect cleavage in one direction, which gives it a micaceous appearance. Its brownish streak is also a diagnostic feature. ## Distinguishing from Similar Minerals It can be confused with other black, platy minerals, such as some micas (e.g., biotite) or hematite. However, it is distinguished by its higher density, brownish streak (hematite has a reddish-brown streak), and specific occurrence environment (oxidation zones of polymetallic deposits). ## Crystal Forms Crystals are typically tabular, flattened parallel to the cleavage plane {100}. They often form radial aggregates, rosettes, or irregular clusters of lamellae.

Geological environment

## Genesis Schneiderhöhnite is a secondary mineral, forming in the oxidation zones (gossans) of hydrothermal polymetallic deposits rich in arsenic. It forms as a result of the weathering of primary sulfides and arsenides, mainly tennantite. ## Mineral Associations It most commonly co-occurs with other secondary minerals of the oxidation zone, such as quartz, hematite, goethite, scorodite, beudantite, ludlockite, stottite, and leiteite. Many of these minerals are also rare arsenates. ## Localities The most important and classic locality for schneiderhöhnite is the Tsumeb mine in Namibia, from which the world's best specimens originate. This is its type locality. Beyond Tsumeb, its presence has been reported in very few places worldwide, making it an extremely rare mineral.

Rarity

Very rare

For collectors

## Quality Criteria The most prized schneiderhöhnite specimens are those with well-formed, sharp crystals forming aesthetic, radial aggregates. Contrast with a light matrix rock (most often quartz) significantly enhances the specimen's attractiveness. The size of crystals and aggregates is a key factor influencing value. ## Popular Localities The only source of high-quality collector specimens is the historic Tsumeb mine in Namibia. Specimens from this locality are considered classics and the standard by which all others are judged.

Care and storage

## Cleaning Schneiderhöhnite specimens should be cleaned very carefully, using a soft brush to remove dust. Due to its perfect cleavage, mechanical washing and ultrasonics should be avoided. If liquid is necessary, pure isopropyl alcohol or distilled water is recommended, applied with great delicacy and immediately dried. ## What to Avoid Contact with acids and other chemicals that may react with arsenites should be avoided. The mineral is brittle and susceptible to mechanical damage. It should not be heated or exposed to sudden temperature changes. ## Storage Specimens should be stored in individual, padded boxes to protect them from scratching and impact. Due to its arsenic content, it is advisable to store it out of reach of children and to wash hands after contact with the mineral.

External references

https://www.mindat.org/min-3571.html