Yellowcatite

Chemical formula: KNaFe<sup>3+</sup><sub>2</sub>(Se<sup>4+</sup>O<sub>3</sub>)<sub>2</sub>(V<sup>5+</sup><sub>2</sub>O<sub>7</sub>)·7H<sub>2</sub>O

Yellowcatite is an extremely rare potassium, sodium, and iron selenite-vanadate, forming microscopic, yellow tabular crystals.

## Characteristics Yellowcatite is a mineral from the selenite-vanadate group, distinguished by its complex chemical composition. It occurs as extremely small, tabular crystals not exceeding 0.2 mm in size. These crystals form dispersed aggregates or rosettes on the surface of the host rock, which is typically mudstone. Due to its microscopic size, its visual features are only discernible under high magnification. ## Physical Properties Yellowcatite crystals are very brittle. They exhibit yellow pleochroism. Hardness and density have not been precisely measured due to the small quantity and size of available material. The luster is described as vitreous to pearly. ## Colors and Varieties This mineral occurs in a uniform, pale yellow color. No color varieties or commercial varieties are known. ## History and Name Yellowcatite was described as a new mineral in 2024 by Anthony R. Kampf and his team. The name comes from its discovery locality – the Yellow Cat uranium mine in Grand County, Utah, USA. This is the only known occurrence of this mineral in the world (type locality). ## Applications Yellowcatite has no industrial application. Its significance is purely scientific and collectible, as a unique and newly discovered mineral species.

Properties

Luster
Vitreous to Pearly
Streak
Yellow
Cleavage
Perfect on {0001}
Fracture
Brittle
Transparency
Transparent
Crystal system
Trigonal

Diagnostic features

## Identification Identification of yellowcatite is impossible without advanced laboratory equipment. Preliminary identification in a collection is based on visual analysis under a microscope: searching for pale yellow, tabular crystals on mudstone originating from the type locality. Final confirmation requires chemical analysis (EDS) and X-ray diffraction (XRD). ## Distinguishing from Similar Minerals This mineral can be confused with other secondary yellow uranium and vanadium minerals, such as carnotite, tyuyamunite, or metatyuyamunite, which often co-occur in the same locality. Differentiation is based on crystal habit (yellowcatite forms thin tablets) and confirmation of selenium in its chemical composition, which is its distinguishing feature. ## Crystal Forms Yellowcatite crystallizes in the form of very thin, tabular crystals with a hexagonal outline. These crystals often form small, loose aggregates or rosettes.

Geological environment

## Genesis Yellowcatite is a secondary mineral that formed as a result of the weathering of primary minerals in an environment rich in selenium, vanadium, and iron. It forms in voids and on fracture surfaces in mudstones of the Brushy Basin Member, part of the Morrison Formation. ## Mineral Associations This mineral co-occurs with a number of other rare secondary minerals, such as carnotite, tyuyamunite, metatyuyamunite, rossite, as well as gypsum and quartz. ## Localities The only confirmed occurrence of yellowcatite in the world is the Yellow Cat mine in the Thompsons district, Grand County, Utah, USA.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a specimen depends on the quantity and quality of microscopic crystals on the rock matrix. The most desirable specimens are those with clearly formed, undamaged crystals forming rich clusters or aesthetic rosettes. The size of the matrix is not critical; what matters is the richness and state of preservation of the yellowcatite crystals themselves. ## Popular Localities The only source of specimens is the type locality – the Yellow Cat mine in Utah, USA. Material from this location is highly sought after by collectors specializing in rare minerals and "micromounts."

Care and storage

## Cleaning Yellowcatite specimens should not be cleaned mechanically or chemically. Any attempts at cleaning, even with water, can irreversibly damage the microscopic crystals. Only dust removal using a gentle stream of compressed air from a safe distance is recommended. ## What to Avoid Avoid contact with water, chemicals, as well as any vibrations and impacts. The crystals are extremely brittle and susceptible to mechanical damage. Do not expose the specimen to extreme temperatures. ## Storage Specimens should be stored exclusively in specialized, sealed "micromount" boxes that protect against dust, moisture, and mechanical damage. Store in stable conditions, away from sources of vibration.

Sources

Read more