Shumwayite

Chemical formula: (U⁶⁺O₂)₂(S⁶⁺O₄)₂·₅H₂O

Shumwayite is a very rare, secondary uranium mineral, forming microscopic, pale greenish-yellow acicular crystals.

## Characteristics Shumwayite is a hydrated uranyl sulfate, occurring as very fine, acicular or fibrous crystals. It typically forms small, radial aggregates or crusts on host rocks. Due to the microscopic size of its crystals, its visual features are difficult to observe without magnification. It is a transparent to translucent mineral. ## Physical Properties This mineral is characterized by low hardness, 2 on the Mohs scale, which means it is very soft. Its density, calculated from the formula and unit cell parameters, is 3.844 g/cm³. It has a white streak. ## Colors and Varieties Shumwayite occurs in one characteristic color – pale greenish-yellow. No color or commercial varieties are distinguished for it. ## History and Name The mineral's name honors George Shumway (born 1930), an American geologist and former employee of the United States Atomic Energy Commission. It was approved as a new mineral species by the International Mineralogical Association (IMA) in 2016 (IMA2016-068). Its discovery was made on samples from two mines in San Juan County, Utah, USA: Giveway-Simplot and Green Lizard. ## Uses Due to its extreme rarity and microscopic size, shumwayite has no industrial applications. It is of purely scientific significance and is of interest to specialized collectors of uranium minerals.

Properties

Mohs hardness: 2
Luster: Vitreous
Streak: White
Density: 3.844
Cleavage: {011}
Fracture: Irregular/Uneven
Transparency: Transparent,Translucent
Crystal system: Monoclinic

Diagnostic features

## Identification Field identification of shumwayite is practically impossible. In a collection, it is recognized by characteristic, pale greenish-yellow, acicular or fibrous aggregates on the host rock, originating from known localities. Definitive identification requires advanced analytical methods, such as X-ray diffraction (XRD) or spectroscopy. ## Distinguishing from Similar Minerals Shumwayite can be confused with many other secondary uranium minerals of similar color and form, such as zippeite, uranophane, or meta-autunite. Distinguishing it from these minerals based on visual characteristics is unfeasible and requires specialized laboratory analysis. ## Crystal Forms This mineral forms very fine, acicular crystals that combine into radial or tangled aggregates. It also occurs as thin crusts and coatings on rock surfaces.

Geological environment

## Genesis Shumwayite is a secondary mineral, forming in the oxidation zones of uranium deposits. It forms as a result of weathering and alteration of primary uranium minerals, such as uraninite, in the presence of sulfate-rich waters. Its formation is associated with dry, desert climates, where minerals can crystallize from solutions on the walls of mine workings. ## Mineral Associations This mineral co-occurs with other secondary uranium sulfates and silicates. At its type locality, it was found in association with gypsum, johannite, zippeite, uranopilite, as well as newly discovered minerals such as redcanyonite and leesite. ## Localities Shumwayite is an extremely rare mineral, known only from two adjacent mines in the Red Canyon district, San Juan County, Utah, USA. These are the Giveway-Simplot and Green Lizard mines, which constitute its type locality.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a shumwayite specimen is primarily assessed based on the richness and visibility of the crusts. The most desirable samples are those where microscopic, acicular crystals form dense, brightly colored aggregates, contrasting with the darker host rock. Due to its microscopic nature, the size of individual crystals is not a key criterion. ## Popular Localities The only source of shumwayite specimens on the collector's market are its two type localities in Utah, USA: the Giveway-Simplot and Green Lizard mines. Specimens from these locations are highly valued by specialists collecting uranium minerals.

Care and storage

## Cleaning Specimens containing shumwayite should generally not be wet cleaned. Due to its fragility and water solubility, any attempt at cleaning may destroy the crystals. Only gentle dust removal with a soft brush or a photographic air blower is permissible. ## What to Avoid Contact with water and other liquids that can dissolve the mineral must be strictly avoided. As a uranium mineral, it is radioactive – inhalation of dust and direct skin contact should be avoided. It requires careful handling, in accordance with safety regulations for radioactive materials. ## Storage Specimens should be stored in closed, airtight containers (so-called perky boxes) to protect them from dust, moisture, and mechanical damage. Due to its radioactivity, it should be kept away from other radiation-sensitive minerals and in a location with limited human exposure.