Natromarkeyite

Chemical formula: Na₂Ca₈(U₆+O₂)₄(CO₃)₁₃(H₂O)₂₄·₃H₂O

Natromarkeyite is a rare, secondary uranyl mineral, forming bright yellow, acicular crystals and coatings in uranium mines.

## Characteristics Natromarkeyite is a complex, hydrated sodium, calcium, and uranyl carbonate. It occurs as fine, acicular or hair-like crystals, which often form radial aggregates, rosettes, as well as fluffy or felt-like coatings and crusts. Individual crystals are typically microscopic in size, rarely exceeding 1 mm in length. Due to its delicate nature, specimens are extremely fragile. ## Physical Properties Natromarkeyite crystals exhibit a bright yellow to greenish-yellow luster, described as silky or dull in the case of dense aggregates. The mineral is translucent. It is a very soft and light mineral, with a calculated density of approximately 2.55 g/cm³. It shows strong, bright green fluorescence under shortwave ultraviolet (UV-SW) light. ## Colors and Varieties This mineral occurs in shades from bright yellow to greenish-yellow. No named varieties have been distinguished. ## History and Name Natromarkeyite was described as a new mineral species in 2019 by Travis A. Olds, Jakub Plášil, Anthony R. Kampf, Owen M. Mills, and Joe Martyl. Its name refers to its chemical composition – the presence of sodium (Latin: *natrium*) – and its structural and chemical similarity to markeyite. It was approved by the International Mineralogical Association (IMA) under number IMA2018-101. The type locality (locus typicus) is the Markey Mine in San Juan County, Utah, USA. ## Uses Natromarkeyite, as a rare mineral occurring in microscopic quantities, has no industrial application. It is of scientific importance only and is sought after by specialized collectors of uranium minerals and rare species.

Properties

Mohs hardness: 2
Luster: Silky
Streak: Light yellow
Density: 2.55
Cleavage: None
Fracture: Uneven
Transparency: Translucent
Crystal system: Monoclinic

Diagnostic features

## Identification Characteristic features of natromarkeyite include its bright yellow color, habit in the form of fluffy, felt-like, or radial aggregates composed of fine needles, and occurrence in paragenesis with other secondary uranium minerals. A key diagnostic feature is its strong, bright green fluorescence under shortwave UV light. ## Distinguishing from Similar Minerals Natromarkeyite is visually almost identical to markeyite. Distinguishing these two minerals is impossible without advanced chemical analyses (EDS) or crystallographic analyses (PXRD) that can confirm the dominance of sodium over calcium in the appropriate structural position. It can also be confused with other acicular, secondary uranyl minerals such as agricolaite or andersonite, from which it is distinguished by its specific genesis and mineral paragenesis. ## Crystal Forms Crystals are very fine, acicular or hair-like, elongated along the [010] axis. They usually form rosette-like, radial, or chaotic, tangled aggregates resembling felt or cotton wool. They also occur as thin crusts and coatings on the host rock.

Geological environment

## Genesis Natromarkeyite is a secondary mineral, forming in the oxidation zone of uranium deposits. It forms as a result of post-mining processes on the walls and wooden supports of mine workings, under conditions of low temperature and high humidity. It originates from the interaction of sodium- and carbonate-rich waters with primary uranium minerals, such as uraninite. ## Mineral Associations This mineral co-occurs with other secondary uranium minerals. At the type locality (Markey Mine), it was found in association with gypsum, calcite, markeyite, agricolaite, andersonite, liebigite, schröckingerite, bayleyite, and uraninite. ## Localities Confirmed occurrences of natromarkeyite are extremely rare. The most important ones include: - **USA** - Markey Mine, Red Canyon, San Juan County, Utah (type locality). - **Czech Republic** - Svornost Mine in Jáchymov, Ore Mountains (the second confirmed occurrence worldwide).

Rarity

Very rare

For collectors

## Quality Criteria The most prized natromarkeyite specimens are those that possess rich, dense coverings of fine, but well-visible crystals on a small rock matrix. Intense, bright yellow color and a distinct, radial structure of aggregates enhance their attractiveness. Due to the microscopic size of the crystals, clarity and transparency are not key criteria. However, the aesthetics of the overall composition and the absence of damage to the delicate needles are important. ## Popular Localities The vast majority, if not all, specimens available on the collector's market come from the type locality – the Markey Mine in Utah, USA. Specimens from Jáchymov, Czech Republic, are extremely rare in collections.

Care and storage

## Cleaning Natromarkeyite specimens should generally not be wet cleaned. Due to its water solubility and extreme fragility, any attempt at cleaning can destroy the delicate crystals. Only very careful dust removal with a soft brush or a photographic air blower is permissible. ## What to Avoid Contact with water, acids, and other chemicals that can dissolve the mineral should be strictly avoided. Specimens are very fragile and sensitive to shocks and touch. As a uranium mineral, it is radioactive and requires safe handling – avoid inhaling dust and wash hands after any contact. ## Storage Natromarkeyite should be stored in closed, stable containers (e.g., "perky boxes") to protect it from mechanical damage, dust, and moisture. It should be kept away from sources of vibration and places where it might be accidentally touched. Due to its radioactivity, it should be stored away from areas of permanent human presence.

Sources

IMA Mineral List (CNMNC)