Hydroredmondite

Chemical formula: [Pb²⁺₈O₂Zn²⁺(OH)₆](S⁶⁺O₃S²⁻)₄·2H₂O

Hydroredmondite is a newly discovered, extremely rare lead-zinc sulfate-sulfide mineral, found in the Redmond mine in Arizona.

## Characteristics Hydroredmondite is a secondary mineral that forms extremely small, tabular or bladed crystals, rarely exceeding 20 micrometers in length. They typically occur as rosetted or tangled aggregates. Due to the microscopic size of the crystals, its visual characteristics are difficult to assess without specialized equipment. ## Physical Properties The crystals are flexible and exhibit perfect cleavage. Hardness and density have not been precisely measured due to the small quantity and size of the material. The luster is described as pearly to vitreous. ## Colors and Varieties This mineral is colorless. No varieties are known. ## History and Name Hydroredmondite was officially recognized by the International Mineralogical Association (IMA) in 2023 under number IMA2023-090. Its name refers to its structural and chemical similarity to redmondite and to the presence of water in its structure. It was discovered in the Redmond mine in Haywood County, North Carolina, USA, which is its type locality. ## Uses Due to its extreme rarity and microscopic size, hydroredmondite has no commercial or industrial applications. It is solely an object of scientific interest and a collector's item for specialized institutions.

Properties

Mohs hardness
2-0
Color
colorless
Luster
Pearly to vitreous
Streak
white
Density
5.124
Cleavage
good on <mi>{101} and {10_1}</mi>
Fracture
Step-Like
Transparency
Transparent
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of hydroredmondite is possible only through advanced analytical methods, such as Raman spectroscopy and single-crystal X-ray diffraction (SC-XRD), which allow for the determination of its chemical composition and crystal structure. Visual identification in the field or even in a collection is impossible. ## Differentiation from Similar Minerals It can be confused with other microscopic, colorless secondary lead minerals, such as redmondite, anglesite, or cerussite. Differentiation requires specialized chemical and structural analysis, as hydroredmondite is distinguished by a unique combination of sulfate and sulfide groups in its structure. ## Crystal Forms It forms very small, thin, tabular crystals with an elongated, bladed shape. These crystals often combine into rosetted or haphazardly tangled aggregates.

Geological environment

## Genesis Hydroredmondite is a secondary mineral, forming in the oxidation zone of polymetallic deposits. In its type locality (Redmond mine), it formed in voids within quartz, as a result of the weathering of primary sulfides, mainly galena. ## Mineral Associations This mineral occurs in association with other secondary lead and zinc minerals. In its type locality, it was found in association with redmondite, anglesite, cerussite, hydrocerussite, linarite, sphalerite, galena, pyromorphite, and quartz. ## Localities The only confirmed occurrence of hydroredmondite in the world is its type locality: Redmond mine, Haywood County, North Carolina, USA.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a hydroredmondite specimen is assessed primarily based on the richness and abundance of microscopic crystals on the rock matrix. Specimens with well-visible crystal aggregates clearly separated from other associated minerals are most highly valued. Due to its microscopic nature, the purity and size of individual crystals are of secondary importance. ## Popular Localities The only source of specimens is the Redmond mine in North Carolina, USA. Material from this locality is highly sought after by collectors specializing in rare and "micromount" minerals.

Care and storage

## Cleaning Specimens containing hydroredmondite, due to their extreme delicacy and microscopic size, should not be cleaned mechanically or chemically. Any attempt at cleaning risks irreversible damage to the mineral. They should be treated solely as objects for microscopic observation. ## What to Avoid Contact with any liquid, including water and alcohols, should be avoided. Touching the surface of the specimen, using ultrasonics, chemical agents, and exposure to extreme temperatures and humidity are also inadvisable. ## Storage Specimens should be stored under stable conditions, in closed, padded "micromount" boxes, protecting them from dust, vibrations, and direct light. The safest method is to store them in the original container in which the specimen was acquired.

External references

Sources

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