Vicanite-(Ce)

Chemical formula: (Ca,Ce<sup>3+</sup>,La<sup>3+</sup>,Th<sup>4+</sup>)<sub>15</sub>As<sup>5+</sup>(As<sup>3+</sup>,Na)<sub>0.5</sub>Fe<sup>3+</sup><sub>0.7</sub>Si<sub>6</sub>B<sub>4</sub>(O,F)<sub>47</sub>

Vicanite-(Ce) is a rare calcium and cerium borosilicate, forming small, prismatic crystals with a vitreous luster and a yellowish-brown color.

## Characteristics Vicanite-(Ce) is a complex borosilicate from the vicanite group, containing calcium, cerium, lanthanum, thorium, arsenic, and silicon. It occurs as small, hexagonal, prismatic crystals, rarely exceeding 1 mm in length. It typically forms radial aggregates or appears as single crystals embedded in the rock. It is a brittle mineral. ## Physical Properties The mineral has a hardness ranging from 5.5-6.5 on the Mohs scale. It exhibits a vitreous luster and is transparent to translucent. Its density is relatively high, approximately 4.85 g/cm³. ## Colors and Varieties The typical color of Vicanite-(Ce) is yellow to yellowish-brown. Some specimens may show subtle pleochroism in shades of yellow. No named varieties of this mineral have been distinguished. ## History and Name The mineral's name comes from its type locality – the Vico volcanic complex in Lazio, Italy. The suffix -(Ce) in the name indicates the dominance of cerium among the rare earth elements in its chemical composition. The mineral was first described in 1991 by a team of researchers: G. Della Ventura, G.C. Parodi, F. Stoppani, and F. Burragato.

Properties

Mohs hardness
5.5-6.5
Luster
Vitreous
Streak
White
Density
4.85
Cleavage
None
Fracture
Conchoidal
Transparency
Transparent to translucent
Crystal system
Trigonal

Diagnostic features

## Identification Amateur identification of Vicanite-(Ce) is practically impossible and requires advanced analytical methods, such as X-ray spectroscopy (EDS/WDS). Preliminary identification is based on observing small, yellowish-brown, hexagonal crystals in a characteristic geological environment (sanidinite blocks in volcanic tuffs). ## Differentiation from Similar Minerals It can be confused with other rare minerals from the vicanite group or other small, yellow silicates occurring in similar parageneses, such as ekanite. Definitive differentiation is only possible through chemical analysis. ## Crystal Forms It forms short, prismatic crystals with a hexagonal cross-section, terminated by a hexagonal pyramid. It often occurs in the form of radial aggregates.

Geological environment

## Genesis It is a mineral of volcanic origin. It forms during the late stages of crystallization in miarolitic cavities within sanidinite blocks ejected during volcanic eruptions. Its formation environment consists of alkali-rich and rare-earth-element-rich volcanic rocks. ## Mineral Associations It co-occurs with minerals such as sanidine, pyroxene, biotite, titanite, apatite, hellandite-(Ce), and other rare minerals from the vicanite group. ## Localities The most important and type locality is Tre Croci, near Vetralla, in the Vico volcanic complex in the province of Viterbo (Lazio, Italy). This is the only confirmed and well-documented locality for this mineral in the world.

Rarity

Very rare

For collectors

## Quality Criteria The quality of Vicanite-(Ce) collector specimens primarily depends on the size and development of the crystals. The most prized specimens are those with sharp, well-formed, transparent crystals of intense yellowish-brown color, set on a contrasting matrix (most often white sanidine). The presence of associated minerals is also important. ## Popular Localities The only source of collector specimens is the type locality in Tre Croci, Italy. All specimens available on the market originate from this single location.

Care and storage

## Cleaning Cleaning with compressed air is recommended to remove dust. Due to the mineral's rarity and fragility, contact with water and any chemical agents should be avoided. ## What to Avoid Avoid ultrasonic cleaners, sudden temperature changes, and contact with acids and other chemicals that can damage the delicate crystals. The mineral contains arsenic and thorium, so avoid inhaling dust and wash hands after handling the specimen. ## Storage Vicanite-(Ce) specimens should be stored in stable conditions, in sealed containers or display cases, away from direct sunlight and moisture. It is best to store them in their original "micromount" box to protect them from mechanical damage.

Sources

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