Owyheeite

Chemical formula: Ag₁+₃Pb₂+₁₀Sb₃+₁₁S₂-₂₈

Owyheeite is a rare sulfosalt mineral of silver, lead, and antimony, forming characteristic acicular crystals with a metallic luster.

## Characteristics Owyheeite is a complex sulfosalt mineral belonging to the lillianite group. It most commonly occurs as aggregates of fine, acicular or capillary crystals, which can form tangled, felt-like masses. Less frequently, better-formed, prismatic crystals up to several centimeters long are found. Its appearance is typical of many sulfosalts – it has a steel-gray to silvery-white color and a strong, metallic luster, which dulls on weathered surfaces and may be covered with a black or yellowish tarnish. ## Physical Properties This mineral is relatively soft, with a Mohs hardness of 2.5, meaning it can be scratched with a fingernail. It is opaque and quite heavy due to its high lead content – its density ranges from 6.45 to 6.58 g/cm³. The crystals are flexible but inelastic, meaning they can be bent but do not return to their original shape. It exhibits perfect cleavage in one direction. ## Colors and Varieties Owyheeite typically ranges in color from light, steel-gray to silvery-white. Over time, its surface may darken, taking on a dull, black hue, and sometimes an iridescent patina or yellowish tarnish from secondary minerals appears. No distinct color varieties or commercial names are recognized. ## History and Name The mineral was first described in 1921 by E.V. Shannon based on samples from the Poorman mine in Owyhee County, Idaho, USA. Its name comes directly from its type locality – Owyhee County, which in turn was named after three native Hawaiians (then called "Owyhee") who disappeared while exploring the region in 1819. ## Uses Due to its rarity, owyheeite has no industrial significance as an ore of silver or lead. It is solely an object of interest for collectors specializing in mineral systematics, especially rare sulfosalts.

Properties

Mohs hardness: 2.5
Luster: Metallic
Streak: Black
Density: 6.45-6.58
Cleavage: Perfect on {010}
Fracture: Uneven
Transparency: Opaque
Crystal system: Monoclinic

Diagnostic features

## Identification Owyheeite can be identified by its characteristic form – tangled aggregates of thin, acicular or capillary crystals. Key features also include its steel-gray color, strong metallic luster, low hardness (2.5 on the Mohs scale), and black streak. It is heavy for its appearance due to its high lead content. ## Distinguishing from Similar Minerals Owyheeite is difficult to distinguish from other acicular sulfosalts without advanced analysis (XRD, EDS). It can be confused with jamesonite, boulangerite, zinkenite, or stibnite. - **Jamesonite** often forms similar "felt-like" aggregates, but its crystals can be thicker and tend to show transverse striations. It also has a slightly higher hardness. - **Boulangerite** also forms acicular aggregates, but they are often more silky in appearance. - **Stibnite** has a similar appearance and luster but is significantly softer (hardness 2) and has perfect cleavage, which causes crystals to easily separate into longitudinal fibers. It also typically forms thicker, better-formed crystals. Final identification requires chemical analysis to confirm the presence of silver, lead, and antimony in appropriate proportions. ## Crystal Forms Owyheeite crystals are elongated in the form of needles, hairs, or rods, often with a square or rectangular cross-section. They usually occur as dense, tangled, or radial aggregates. Single, well-formed crystals are rarely found.

Geological environment

## Genesis Owyheeite is a hydrothermal mineral. It forms in ore veins under low to moderate temperature conditions. It is a product of crystallization from solutions rich in sulfur, antimony, lead, and silver. ## Mineral Associations This mineral often co-occurs with other sulfides and sulfosalts. Its most common associated minerals include: quartz, pyrite, galena, sphalerite, stibnite, jamesonite, boulangerite, tetrahedrite, polybasite, and various silver minerals such as acanthite or pyrargyrite. ## Localities The most important and classic occurrences of owyheeite are in the USA, in silver-bearing veins in Idaho (Owyhee County, including the Poorman and De Lamar mines) and Nevada. It is also known from historical silver mines in Mexico (e.g., Zacatecas). In Europe, its occurrences have been noted in Příbram in the Czech Republic, in mines in Romania (Baia Sprie, Herja), as well as in Germany and Slovakia. It also occurs in Bolivia (Potosí department).

Rarity

Rare

For collectors

## Quality Criteria The most valued specimens by collectors are those with well-formed, long, and undamaged crystals, forming aesthetic, radial or tangled aggregates. Contrast with a light matrix, most often quartz, significantly enhances visual appeal. Specimens from historical, classic localities, such as the Poorman mine in Idaho, are particularly sought after. The purity of the specimen, absence of mechanical damage, and undesirable tarnish also affect its value. ## Popular Localities Specimens from the type locality in Owyhee County, Idaho, USA, are considered the best in the world. High-quality collector material was also supplied by mines in the Czech Republic (Příbram) and Romania (especially from the Herja mine). Specimens from these locations are the standard against which finds from other parts of the world are compared.

Care and storage

## Cleaning Owyheeite specimens are very delicate and brittle. To remove dust, use only a soft brush or compressed air from a safe distance. Wet cleaning, especially with detergents, is not recommended, as they may react with the mineral. ## What to Avoid Avoid contact with chemicals, acids, and bases. The mineral is sensitive to moisture and temperature changes. Prolonged exposure to light and humid air can cause oxidation, dulling, and the formation of tarnish. It should not be heated or exposed to ultrasound. ## Storage It is recommended to store specimens in closed, dry containers (e.g., membrane boxes or mineralogical display cases) away from direct sunlight and heat sources. Due to the fragility of acicular crystals, avoid vibrations and contact with harder minerals.

Sources

IMA Mineral List (CNMNC)