Arsenoflorencite-(Ce)

Chemical formula: Ce₃+Al₃(As₅+O₄)₂(OH)₆

Arsenoflorencite-(Ce) is a rare mineral from the alunite supergroup, a lanthanide and aluminum arsenate, forming small trigonal crystals of straw-yellow or pinkish color.

## Characteristics Arsenoflorencite-(Ce) is the arsenate analog of florencite-(Ce), belonging to the alunite supergroup. It most often forms small, well-developed rhombohedral crystals, which can be so modified as to become pseudocubic. It also occurs in granular aggregates, crusts, and earthy masses. It is a brittle mineral, and its specimens are usually small, often microminerals. ## Physical Properties The Mohs hardness is 3.5, making it a relatively soft mineral. It has a vitreous to resinous luster. It is translucent to opaque. The calculated density is approximately 4.08 g/cm³. ## Colors and Varieties This mineral ranges in color from pale yellow and straw-yellow, through yellowish-brown, to pinkish. No distinct color varieties or commercial forms are recognized. Changes in the composition of rare earth elements lead to the formation of other minerals in this series, such as arsenoflorencite-(Nd) or arsenoflorencite-(La). ## History and Name The name refers to its chemical composition (dominance of arsenic) and its structural similarity to florencite. The suffix -(Ce) indicates that cerium is the dominant rare earth element in this mineral. It was first described in 1985 by a team of Russian mineralogists led by I. B. Nickol'skaya. The type locality is the Cherkasar deposit in the Kurama Mountains, Uzbekistan. ## Applications Arsenoflorencite-(Ce) has no industrial applications. It is solely an object of interest for scientists and collectors of rare minerals and microminerals.

Properties

Mohs hardness: 3.5
Luster: Vitreous to resinous
Streak: White
Density: 4.08
Cleavage: Good on {0001}
Fracture: Conchoidal
Transparency: Translucent to opaque
Crystal system: Trigonal

Diagnostic features

## Identification Helpful identification features include: characteristic crystal habit (sharp rhombohedra or pseudocubes), relatively low hardness, color, and occurrence environment. However, definitive identification is impossible without advanced chemical analyses (e.g., EDS) to confirm the presence of cerium, aluminum, and arsenic. ## Distinguishing from Similar Minerals Arsenoflorencite-(Ce) is visually almost indistinguishable from other members of the alunite-jarosite group, such as florencite-(Ce) (its phosphate analog), beudantite and segnitite (containing lead and iron), or dussertite (containing barium). The differences between them are chemical. It may also resemble mimetite, which, however, crystallizes in the hexagonal system and has a higher density. ## Crystal Forms It most often forms small, but well-developed rhombohedral crystals, often appearing cubic (pseudocubic). It is also found in granular aggregates, radial aggregates, and as earthy coatings and encrustations.

Geological environment

## Genesis It is a secondary mineral, forming in the oxidation (weathering) zones of ore deposits. It forms as a result of the reaction of arsenic-rich solutions (derived from the decomposition of primary arsenides, e.g., arsenopyrite) with minerals containing aluminum and rare earth elements. It also occurs in laterites and carbonatites. ## Mineral Associations It co-occurs with other secondary minerals, such as quartz, kaolinite, goethite, hematite, dussertite, beudantite, segnitite, as well as other arsenates and phosphates of rare earth elements. ## Localities Key localities for this mineral include the Cherkasar deposit in Uzbekistan (type locality), the Brewer mine in South Carolina (USA), the Kintore opencut in Broken Hill (Australia), the Talmessi mine (Iran), and the Clara mine in the Black Forest (Germany), famous for its microminerals.

Rarity

Rare

For collectors

## Quality Criteria For collectors, the most desirable specimens are those with sharp, well-formed crystals, even if they are microscopic in size. Intense, attractive color (e.g., pink or vivid yellow) and the placement of crystals on a contrasting rock matrix are valued. The co-occurrence with other rare secondary minerals enhances the value of a specimen. ## Popular Localities Specimens from localities known for excellent microcrystals, such as the Clara mine in Germany or the Kintore Opencut in Australia, are considered the best for collectors. These localities provide specimens of high aesthetic and scientific value.

Care and storage

## Cleaning Specimens should be cleaned very carefully, using a soft brush and distilled water. Due to its low hardness, the mineral is susceptible to scratching. Ultrasonic cleaners or strong water jets should not be used. ## What to Avoid As an arsenate, it is sensitive to acids. Contact with chemicals, high temperatures, and sudden temperature changes should be avoided. Due to its arsenic content, inhaling dust should be avoided, and hands should be washed after handling raw specimens. ## Storage It is recommended to store specimens in separate, sealed display boxes to prevent scratching by harder minerals. Protect from dust and moisture. No special lighting conditions are required.

Sources

IMA Mineral List (CNMNC)