Wupatkiite

Chemical formula: Co<sup>2+</sup>Al<sub>2</sub>(S<sup>6+</sup>O<sub>4</sub>)<sub>4</sub>·22H<sub>2</sub>O

Wupatkiite is a very rare, hydrated cobalt and aluminum sulfate, forming microscopic, pink, acicular crystals.

## Characteristics Wupatkiite is a mineral from the sulfate group, chemically classified as a hydrated cobalt and aluminum sulfate. It occurs as extremely small, acicular or hair-like crystals, rarely exceeding 1 mm in length. These crystals form delicate, radial aggregates or tangled, felt-like masses. Due to their size, individual crystals are usually visible only under a microscope. ## Physical Properties Wupatkiite crystals are flexible and can be bent. This mineral is characterized by a vitreous luster. Its hardness and density have not been precisely measured due to the small size and fragility of the crystals. ## Colors and Varieties Wupatkiite has a characteristic pink to pinkish-purple color. No varieties have been distinguished. ## History and Name The mineral was discovered in Cameron (Coconino County, Arizona, USA), within the Wupatki National Monument, from which its name is derived. It was described and approved as a new mineral by the International Mineralogical Association (IMA) in 1994. Its discoverers were J.E. Doughty and P.A. Doughty.

Properties

Luster
Vitreous
Streak
White
Cleavage
Perfect on {010}
Fracture
Uneven
Transparency
Transparent
Crystal system
Monoclinic

Diagnostic features

## Identification Characteristic features of wupatkiite include its pink color, acicular or fibrous crystal habit, and occurrence as small, radial aggregates. The locality and co-occurring minerals, such as cobaltian pickeringite, are also crucial for identification. ## Distinguishing from Similar Minerals Wupatkiite can be confused with other pink, acicular sulfates, especially cobaltian pickeringite, with which it often co-occurs. Final differentiation requires advanced analytical methods, such as X-ray diffraction (XRD) or chemical analysis (EDS/WDS). ## Crystal Forms This mineral forms very fine, acicular or hair-like crystals, elongated along the [001] axis. These crystals combine into radial, stellate aggregates or tangled, felt-like masses.

Geological environment

## Genesis Wupatkiite is a secondary mineral, formed as a result of weathering (oxidation) processes of cobalt sulfides in a dry and desert climate. It forms as efflorescences on the walls of sedimentary rocks (mudstones and sandstones), in places protected from direct rain, such as rock overhangs or entrances to old mines. ## Mineral Associations This mineral most commonly co-occurs with cobaltian pickeringite, as well as with gypsum, alunogen, melanterite, epsomite, and morenosite. ## Localities The most important and type locality for wupatkiite is the Wupatki National Monument in Arizona, USA. It has also been identified in several other locations worldwide, including the Svornost mine in Jáchymov (Czech Republic) and the Cobalt-Gowganda area in Ontario (Canada).

Rarity

Very rare

For collectors

## Quality Criteria The quality of wupatkiite specimens is assessed based on the richness and aesthetics of the crystal aggregates. Specimens with well-formed, radial clusters of intense pink color, contrasting with the host rock, are most valued. Due to the microscopic size of the crystals, the size of individual needles is not a key criterion; rather, the abundance and coverage of the rock surface are important. ## Popular Localities By far the most desirable and classic specimens come from the type locality, the Wupatki National Monument in Arizona, USA. Specimens from other confirmed localities, such as Jáchymov, are also valued by collectors specializing in rare and systematic minerals.

Care and storage

## Cleaning Wupatkiite specimens are extremely delicate and sensitive to water. They should not be cleaned wet. Any contaminants, such as dust, can only be removed using compressed air from a safe distance or very carefully, using a soft brush. ## What to Avoid Contact with water must be absolutely avoided, as it can dissolve or damage the microscopic crystals. The mineral is sensitive to changes in humidity and temperature. It should not be heated or exposed to chemicals. Due to its fragility, all shocks and touching should be avoided. ## Storage Wupatkiite specimens should be stored in airtight, sealed containers (so-called "perky boxes") that protect them from dust, mechanical damage, and changes in humidity. It is best to keep them in stable room conditions, away from direct sunlight and heat sources.

Sources

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