Metastibnite

Chemical formula: Sb₃+₂S₂-₃

Amorphous, reddish-orange antimony sulfide, formed mainly by the weathering of stibnite.

## Characteristics Metastibnite is an amorphous (non-crystalline) antimony sulfide, meaning it does not form crystals. It occurs as earthy, powdery, or botryoidal aggregates, as well as coatings and crusts on other minerals, primarily stibnite. Its appearance is usually dull and inconspicuous, with its vivid, reddish-orange or red color being its most characteristic visual feature. ## Physical Properties As an amorphous substance, it exhibits no cleavage. Its hardness is low, and its density is approximately 4.88 g/cm³. The luster is typically earthy or dull, and the mineral is opaque. ## Colors and Varieties Metastibnite is uniform in color, ranging from hyacinth red, through reddish-orange, to reddish-brown. No distinct color varieties or commercial types are recognized. ## History and Name The mineral's name refers to its chemical composition and its association with stibnite (Greek *meta* - "after" or "changed" and *stibnite*). It was first described in 1862 by G.E. Moore based on samples from Steamboat Springs, Washoe County, Nevada, USA. It is polymorphic with stibnite, meaning it has the same chemical composition (Sb₂S₃) but a different, amorphous internal structure. ## Uses Metastibnite has no industrial significance. Its role is limited to being an object of interest for collectors specializing in rare minerals or secondary minerals from oxidation zones.

Properties

Mohs hardness: 2
Luster: Earthy
Streak: Orange-red
Density: 4.88
Cleavage: None
Fracture: Uneven
Transparency: Opaque

Diagnostic features

## Identification Metastibnite is most easily recognized by its intense red or reddish-orange color and its earthy, powdery, or botryoidal habit. A key feature is its close association with stibnite, on which it forms characteristic coatings and weathering products. ## Distinguishing from Similar Minerals It can be confused with cinnabar (HgS), which also has a red color and similar hardness. However, cinnabar has a significantly higher density (approx. 8.1 g/cm³) and usually an intensely red streak. Kermesite (Sb₂S₂O) can also be similar, but it forms acicular or radial crystal aggregates, whereas metastibnite is always amorphous. Realgar (As₄S₄) has a similar color but is a crystalline mineral, often forming distinct crystals, and is unstable in light. ## Crystal Forms Metastibnite is an amorphous (non-crystalline) mineral and does not form crystals. It occurs as earthy, powdery, botryoidal aggregates, as well as thin coatings and crusts.

Geological environment

## Genesis Metastibnite is a secondary mineral, formed in the oxidation (weathering) zones of ore deposits containing stibnite (Sb₂S₃). It forms under low-temperature conditions, often as a result of hot spring activity or as a product of stibnite weathering under the influence of surface waters. ## Mineral Associations It most commonly co-occurs with stibnite, which is its parent mineral. It is also accompanied by other minerals of the oxidation zone, such as native sulfur, cinnabar, realgar, as well as various antimony oxides (e.g., stibiconite, valentinite, senarmontite) and sulfates. ## Localities Key localities worldwide include Steamboat Springs, Nevada (USA), where it was discovered; antimony deposits in the Kadamjay region, Kyrgyzstan; Baia Sprie, Romania; and various locations in Bolivia and Japan. It occurs in many places worldwide where stibnite-rich deposits are weathering.

Rarity

Not very common

For collectors

## Quality Criteria The collector appeal of metastibnite primarily depends on the intensity and purity of its red color. The most prized specimens are those where metastibnite forms vivid red, contrasting coatings on well-formed stibnite crystals. The thickness and uniformity of the coating also enhance the specimen's value. Due to its nature, purity and form are not assessed in a traditional manner. ## Popular Localities Classic and valued specimens come from the type locality – Steamboat Springs, Nevada, USA. Specimens from deposits in Kyrgyzstan and Romania (Baia Sprie) are also known for good quality.

Care and storage

## Cleaning Metastibnite specimens are extremely delicate and fragile. Mechanical cleaning is not recommended. Only careful removal of dust with a soft brush or a stream of compressed air from a safe distance is permissible. Avoid contact with water and any chemicals. ## What to Avoid The mineral is sensitive to sunlight, under which it can darken and undergo further transformations. Avoid moisture, high temperatures, and all chemicals, especially acids and bases. Due to its fragility, it should be protected from vibrations and impacts. ## Storage Specimens should be stored in closed, dry containers or display cases, away from direct sunlight and heat sources. It is best to keep it in its original collector's box to minimize the risk of mechanical damage.

Sources

IMA Mineral List (CNMNC)