Schuetteite

Chemical formula: Hg₂+₃O₂(S₆+O₄)

Schuetteite is a very rare, secondary mercury oxy-sulfate, forming characteristic, bright red coatings and crusts.

## Characteristics Schuetteite is a secondary mineral, formed by the oxidation of native mercury and cinnabar. It occurs as microcrystalline, earthy, or powdery coatings and thin crusts. Its most characteristic feature is its intense, bright red to orange-red color. Due to its chemical composition, it is a highly toxic mineral. ## Physical Properties This mineral is very soft, and its aggregates are brittle. The luster is usually dull or earthy, sometimes with a silky luster in the case of fine-fibrous aggregates. It is opaque. Due to its occurrence in the form of thin coatings, precise determination of many physical properties is difficult. ## Colors and Varieties Schuetteite occurs in characteristic shades of red: from bright red, through red-orange, to orange. No color or commercial varieties are distinguished. ## History and Name The mineral is named in honor of Professor Waldemar Henry Schuette (1899-1959), an American mining engineer who first drew attention to this mineral at the Oceanic mine in California. It was described and approved as a new mineral species in 1961 by C.L. Bailey, C.W. Chesterman, and M.C. Stinson. ## Uses Schuetteite has no industrial application. It is of purely scientific and collector's interest, being sought after by specialized collectors of rare minerals.

Properties

Mohs hardness: 2
Luster: Dull
Streak: Orange-red
Density: 8.21
Cleavage: None
Fracture: Earthy
Transparency: Opaque
Crystal system: Trigonal

Diagnostic features

## Identification Schuetteite is primarily recognizable by its bright red color, mode of occurrence (earthy coatings and crusts), and geological environment. It occurs on rocks in the oxidation zones of mercury deposits, often in direct proximity to native mercury or cinnabar. ## Distinguishing from Similar Minerals It can be confused with cinnabar (HgS), which also has a red color. However, cinnabar is usually harder, has a higher density, and often forms better-developed crystals with a adamantine or metallic luster, whereas schuetteite is dull and earthy. It is sometimes confused with other secondary, red mercury minerals, such as eglestonite, but a definitive distinction requires advanced analyses (XRD, EDS). ## Crystal Forms Schuetteite crystals are extremely rare and microscopic in size. It typically forms very fine-grained, earthy, powdery, or dusty aggregates in the form of coatings and thin crusts on the surface of host rocks.

Geological environment

## Genesis Schuetteite is a secondary mineral. It forms in the oxidation zones of mercury deposits, as a result of weathering and alteration of primary mercury minerals, mainly cinnabar (HgS) and native mercury (Hg). It forms under near-surface conditions, under the influence of oxygen- and sulfate-rich waters. ## Mineral Associations It most commonly co-occurs with the minerals from which it forms: native mercury and cinnabar. It is also accompanied by other secondary mercury minerals, such as calomel (Hg₂Cl₂), eglestonite (Hg₂Cl₃O(OH)), terlinguaite (Hg₂ClO), as well as gypsum (CaSO₄·2H₂O) and other sulfates. ## Localities The most important and classic localities for this mineral are in the USA. These include mines in San Benito County, California (e.g., Oceanic mine – type locality, New Idria mine), as well as in the Terlingua district, Texas. It is also known from several other places in the world, including the Monte Amiata mine in Tuscany (Italy) and Almadén in Spain.

Rarity

Very rare

For collectors

## Quality Criteria The most prized schuetteite specimens are those characterized by a large coverage area on the host rock and an intense, bright red color. Contrast with a light host rock (e.g., opal, chalcedony) enhances visual appeal. Due to the microscopic nature of the crystals, their form is not a key criterion. A well-documented locality is also important. ## Popular Localities The most sought-after specimens by collectors come from classic localities in the USA, especially from the Oceanic and New Idria mines in California and the Terlingua region in Texas. Specimens from these locations are considered exemplary for this species.

Care and storage

## Cleaning Schuetteite specimens should generally not be cleaned. Any attempt at mechanical (brush) or chemical (water, solvents) cleaning will almost certainly destroy the delicate coatings. The mineral is extremely brittle. ## What to Avoid Avoid contact with water and chemicals. The mineral is sensitive to abrasion and vibrations. Due to its mercury content, it is highly toxic – avoid inhaling dust and direct skin contact. Wash hands thoroughly after each contact with a specimen. ## Storage Schuetteite specimens should be stored in tightly sealed, transparent containers (so-called micromount boxes), which protect them from mechanical damage and dust, and also prevent accidental contact. The container should be clearly labeled as toxic. Keep away from children and pets.

Sources

IMA Mineral List (CNMNC)