Florencite-(Ce)

Chemical formula: Ce³⁺Al₃(PO₄)₂(OH)₆

Florencite-(Ce) is an aluminum and cerium phosphate, forming small, vitreous crystals ranging in color from pale yellow to reddish-orange.

## Characteristics Florencite-(Ce) is a mineral from the plumbogummite group, belonging to the broader alunite supergroup. Chemically, it is a hydrated aluminum and cerium phosphate. It forms small, well-formed crystals, often with pseudocubic or rhombohedral shapes. It also occurs as granular aggregates, radial aggregates, or as earthy masses. Specimens are usually small, and individual crystals rarely exceed a few millimeters. ## Physical Properties This mineral is characterized by a hardness of 5-6 on the Mohs scale, making it relatively resistant to scratching. It has a vitreous luster, and on fracture surfaces, it can be slightly resinous. It is transparent to translucent. The density is approximately 3.45 g/cm³. ## Colors and Varieties Florencite-(Ce) exhibits a range of colors, most commonly from pale yellow, through buttery yellow, to reddish-orange. Pink, light brown, gray, and even colorless specimens are also found. In thin sections, it is colorless to pale yellow. Color zoning, i.e., concentric bands of varying color saturation, is often observed in crystals. ## History and Name The mineral's name comes from William Florence (1864-1942), a chemist at the United States Department of Agriculture. The suffix "-(Ce)" indicates the dominance of cerium as a rare earth element in its chemical composition. The mineral was first described based on specimens from Mata dos Crioulos in Minas Gerais, Brazil.

Properties

Mohs hardness
5-6
Luster
Vitreous
Streak
White
Density
3.45
Cleavage
Good on {0001}; interrupted on <mi>{11_20}</mi>
Fracture
Splintery,Sub-Conchoidal
Transparency
Transparent,Translucent
Crystal system
Trigonal

Diagnostic features

## Identification Florencite-(Ce) is recognized by its characteristic small, pseudocubic or rhombohedral crystals with a vitreous luster. Its typical colors (yellow, orange, pink) and occurrence in specific geological environments are key indicators. A hardness of 5-6 distinguishes it from many softer phosphates. ## Distinguishing from Similar Minerals It can be confused with other minerals from the plumbogummite group or alunite supergroup, such as goyazite, crandallite, or woodhouseite. Final differentiation from these minerals often requires advanced chemical analyses (e.g., EDS) to determine the dominant rare earth element and chemical composition. Visually, it may resemble some garnets or scheelite, but it differs from them in crystal shape and hardness. ## Crystal Forms It most often forms small, sharp rhombohedral crystals that can mimic cubes (pseudocubic). It also occurs as granular aggregates, rosette-like or radial aggregates, as well as earthy masses and concretions.

Geological environment

## Genesis Florencite-(Ce) is a secondary mineral. It forms in weathering zones of rocks rich in phosphorus and rare earth elements, especially in carbonatites and alkaline pegmatites. It also forms as a result of hydrothermal processes and in alluvial (river) sediments as a heavy mineral resistant to weathering. ## Mineral Associations It often co-occurs with minerals such as monazite, xenotime, bastnäsite, apatite, quartz, kaolinite, goethite, hematite, and other minerals from the alunite supergroup. ## Localities Important world localities include Mata dos Crioulos in Minas Gerais (Brazil), from where the type material originates. It is also known from many localities in the United States (e.g., Big Four Mine in Colorado), Russia (Kola Peninsula), Australia, China, and various African countries, where it occurs in carbonatites and laterites.

Rarity

Not very common

For collectors

## Quality Criteria The most valued by collectors are specimens with sharp, well-formed crystals of intense, attractive color (e.g., orange or pink). Transparency and lack of damage are important. Since crystals are usually small, groups of crystals aesthetically set on a rock matrix are highly prized. Contrast with associated minerals also increases the value of the specimen. ## Popular Localities Collector-grade specimens mainly come from Brazil (Minas Gerais), as well as from some US localities, such as the Big Four Mine in Rock Creek (Colorado), known for its sharp, pseudocubic crystals.

Care and storage

## Cleaning Florencite-(Ce) specimens should be cleaned very carefully, using a soft brush to remove dust. If necessary, distilled water can be used, avoiding prolonged soaking. Ultrasonic cleaners should not be used, as they can damage fragile crystals. ## What to Avoid This mineral is sensitive to strong acids, which can chemically damage it. Avoid sudden temperature changes and prolonged exposure to direct sunlight, which theoretically may affect its color. Due to its good cleavage, it should be protected from impacts and pressure. ## Storage Collector specimens of florencite-(Ce) are best stored in separate, padded boxes or display cases to prevent abrasions and mechanical damage. Due to the small size of the crystals, they are often mounted in "micromount" boxes.

External references

Sources

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