Greenlizardite

Chemical formula: (N³⁻H₄)Na(U⁶⁺O₂)₂(S⁶⁺O₄)₂(OH)₂·₄H₂O

Greenlizardite is a very rare, secondary uranyl mineral, distinguished by its intensely greenish-yellow color and occurrence as microscopic crystals.

## Characteristics Greenlizardite is a hydrated ammonium, sodium, and uranyl hydroxyl sulfate. It occurs as very small, bladed or acicular crystals, rarely exceeding 0.2 mm in length. These crystals form rosette-like aggregates, spherical clusters, or thin coatings on the host rock. Due to their size, individual crystals are usually only visible under a microscope. ## Physical Properties Greenlizardite crystals exhibit a vitreous luster. This mineral is transparent to translucent. Its hardness and density have not been precisely measured due to the small size of the crystals, but the density calculated based on the chemical formula and unit cell parameters is 3.68 g/cm³. ## Colors and Varieties Greenlizardite is characterized by a vivid, greenish-yellow color. No color varieties or commercial varieties are known. ## History and Name The mineral was discovered in the Green Lizard mine, San Juan County, Utah (USA), from which it derives its name. It was described and approved by the International Mineralogical Association (IMA) in 2017. The discovery was made by a team of mineralogists led by Travis A. Olds. ## Applications Greenlizardite, as a uranium mineral, is highly radioactive. It has no industrial applications and is solely of scientific and collector interest, sought after by specialized collectors of uranium minerals.

Properties

Mohs hardness: 2
Color: Light green-yellow
Luster: Vitreous
Streak: White
Density: 3.469
Cleavage: Perfect {001} and good <mi>{2_10}.</mi>
Fracture: Irregular/Uneven
Transparency: Transparent
Crystal system: Triclinic

Diagnostic features

## Identification Greenlizardite is identified by its characteristic, intense greenish-yellow color, specific crystal habit (fine needles and blades forming aggregates), and strong, greenish-yellow fluorescence under shortwave ultraviolet (UV-SW) light. Its origin from oxidized zones of uranium deposits is also key. ## Distinguishing from Similar Minerals It can be confused with other secondary uranyl minerals of similar color, such as johannite, uranopilite, or zippeite. Definitive differentiation requires advanced analytical methods, such as Raman spectroscopy or X-ray diffraction (XRD), due to the microscopic size of the crystals. ## Crystal Forms Crystals are very small, acicular or bladed, elongated along the [100] axis. They typically form radial or rosette-like aggregates, as well as spherical clusters and thin coatings.

Geological environment

## Genesis Greenlizardite is a secondary mineral, forming in the oxidation (weathering) zones of uranium-vanadium deposits. It forms as a result of sulfate-rich waters acting on primary uranium minerals, such as uraninite. Its formation is associated with post-diagenetic processes within sandstone sediments. ## Mineral Associations This mineral co-occurs with other secondary uranyl sulfates, such as johannite, natrozippeite, as well as gypsum, pyrite, and organic matter (charcoal). ## Localities The only confirmed occurrence of greenlizardite in the world is its type locality – the Green Lizard mine, located in White Canyon, San Juan County, Utah, USA.

Rarity

Very rare

For collectors

## Quality Criteria The most valuable greenlizardite specimens are those with rich, well-visible coatings of microcrystalline aggregates on contrasting host rock (usually sandstone). Specimens with clearly formed, though still microscopic, crystal rosettes are highly prized. Due to its rarity, any authentic specimen is considered valuable. ## Popular Localities The only source of specimens is the Green Lizard mine in Utah, USA. Material from this locality is extremely rare and sought after by collectors specializing in uranium minerals and minerals from specific localities (so-called "type locality specimens").

Care and storage

## Cleaning Greenlizardite specimens should not be wet cleaned. Dust can only be removed using a soft brush or a photographic air blower. Due to radioactivity, all activities should be performed with caution, avoiding inhalation of dust. ## What to Avoid Contact with water and chemicals, which can dissolve or damage the microscopic crystals, must be strictly avoided. The mineral is sensitive to heat and can dehydrate. As a uranyl mineral, it is highly radioactive – direct, prolonged contact should be avoided, and it should never be ingested. ## Storage Specimens should be stored in sealed, lead-lined or appropriately shielded containers away from other radiation-sensitive minerals. The container must be clearly marked with a radioactivity symbol. Store in a dry place, away from heat sources and direct sunlight.