Redmondite

Chemical formula: [Pb<sup>2+</sup><sub>8</sub>O<sub>2</sub>Zn<sup>2+</sup>(OH)<sub>6</sub>](S<sup>6+</sup>O<sub>3</sub>S<sup>2-</sup>)<sub>4</sub>

Redmondite is a rare lead mineral, distinguished by a unique combination of sulfate and sulfide in its structure and an intense red color.

## Characteristics Redmondite is a complex lead and zinc sulfato-sulfide. It forms very small, tabular or bladed crystals, rarely exceeding 0.2 mm, which usually occur as radial or tangled aggregates. Its most characteristic feature is an intense, bright red to orange-red color. ## Physical Properties Redmondite crystals exhibit a vitreous to slightly resinous luster. Due to the small size of the crystals, many physical properties, such as hardness or density, have not been precisely determined. The mineral is brittle. ## Colors and Varieties This mineral occurs in a characteristic, bright color range from orange-red to red. No varieties have been distinguished. ## History and Name Redmondite was officially recognized as a new mineral by the International Mineralogical Association (IMA) in 2022 (IMA2022-095). Its name honors Ian R. Redmond, an Australian mineral collector who discovered the first specimens of this mineral in the North Star mine in Beaver County, Utah, USA. The mineral's analysis and description were carried out by a team led by Anthony R. Kampf. ## Uses Redmondite has no industrial application. Its significance is purely scientific and collectible due to its rarity, unique chemical composition, and attractive appearance of microcrystals.

Properties

Mohs hardness
2
Luster
Vitreous to Resinous
Streak
Orange-red
Density
6.86
Cleavage
Perfect on {100}
Fracture
Splintery
Transparency
Translucent
Crystal system
Monoclinic

Diagnostic features

## Identification Redmondite can be identified by its bright red color, characteristic small, tabular crystals forming radial aggregates, and co-occurrence with other rare secondary minerals in the oxidation zones of polymetallic deposits. ## Distinguishing from Similar Minerals It can be confused with other red secondary lead minerals, such as minium or wulfenite. Differentiation requires advanced analytical methods, such as Raman spectroscopy or chemical analysis (EDS), due to the unique presence of both sulfate and sulfide ions in its structure. ## Crystal Forms Crystals are very small, usually less than 1 micrometer thick and up to 0.2 mm long. They have a tabular or bladed habit, often tapering towards the ends. They typically form rosette-like, radial, or tangled aggregates.

Geological environment

## Genesis Redmondite is a secondary mineral, forming in the oxidation zones of polymetallic deposits. It forms as a result of the weathering of primary sulfides, mainly galena, in the presence of zinc. It forms under low-temperature conditions, directly on the surface of other minerals. ## Mineral Associations At the type locality (North Star mine, Utah, USA), it co-occurs with anglesite, lanarkite, leadhillite, susannite, cerussite, hydrocerussite, linarite, munakataite, as well as newly described minerals such as northstarite and kampfite. ## Localities The only confirmed occurrence of redmondite in the world is its type locality: the North Star mine in the Star Mining District, Beaver County, Utah, USA.

Rarity

Extremely rare

For collectors

## Quality Criteria The most valuable specimens are those that possess rich, well-formed, radial aggregates of bright red crystals, contrasting with the rock matrix. Due to the microscopic size of the crystals, the aesthetics of the entire aggregate and its photogenicity under magnification are crucial. Association with other rare minerals from this locality is also important. ## Popular Localities The only source of specimens is the North Star mine in Utah, USA. Material from this location is highly sought after by collectors specializing in rare minerals and "micromounts."

Care and storage

## Cleaning Specimens should be cleaned only very carefully, using compressed air to remove dust. Due to the extreme brittleness and small size of the crystals, any mechanical contact, including with brushes or water, should be avoided. ## What to Avoid Contact with water, chemicals, and ultrasonics must be absolutely avoided. The crystals are very delicate and can be damaged by vibrations, temperature changes, and humidity. Specimens should not be exposed to direct sunlight. ## Storage It is recommended to store redmondite specimens exclusively in specialized "micromount" boxes, which protect them from dust, shocks, and physical contact. Display should take place under stable conditions, away from sources of vibration and humidity.

External references

Sources

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