Rodolicoite

Chemical formula: Fe<sup>3+</sup>PO<sub>4</sub>

Rodolicoite is an extremely rare iron(III) phosphate, forming microscopic, tabular crystals of a brownish color.

## Characteristics Rodolicoite is a mineral from the phosphate group, chemically corresponding to anhydrous iron(III) phosphate. It occurs as extremely small, tabular or platy crystals, reaching sizes up to 100 micrometers in length and only a few micrometers in thickness. These crystals form aggregates or rosette-like clusters. Due to its microscopic size, its visual features are difficult to assess with the naked eye. ## Physical Properties Rodolicoite crystals exhibit a luster described as vitreous to submetallic. They are brittle, and their hardness and density have not been precisely measured due to the small size of the samples. The calculated density is 3.55 g/cm³. ## Colors and Varieties This mineral has a color ranging from brown to reddish-brown. No varieties have been distinguished. ## History and Name Rodolicoite was discovered in fumaroles of the La Fossa volcano on Vulcano island (Aeolian Islands, Italy). It was approved as a new mineral by the International Mineralogical Association (IMA) in 2007. Its name honors the Italian mineralogist and professor of petrography, Francesco Rodolico (1905-1988) from the University of Florence, for his contributions to the mineralogy of Tuscany and research on building materials in Florentine monuments.

Properties

Luster
Vitreous to submetallic
Streak
Brown
Density
3.55
Cleavage
Good on {010}
Fracture
Uneven
Transparency
Translucent to opaque
Crystal system
Orthorhombic

Diagnostic features

## Identification Identification of rodolicoite is possible only through advanced analytical methods, such as Raman spectroscopy and single-crystal X-ray diffraction (XRD), combined with chemical analysis (EDS). Visual identification is impossible due to the microscopic size of the crystals. ## Distinguishing from Similar Minerals It can be confused with other microscopic fumarolic products, such as hematite or other rare phosphates. Certain differentiation requires specialized laboratory equipment. ## Crystal Forms It forms very small, thin, tabular crystals, often elongated and flattened. These crystals group into rosette-like or radial aggregates.

Geological environment

## Genesis Rodolicoite is a mineral of volcanic origin, formed by sublimation from volcanic gases. It crystallizes in high-temperature (400-600°C) fumaroles, depositing directly from the gas phase onto the walls of volcanic conduits. ## Mineral Associations At its type locality (Vulcano, Italy), it co-occurs with hematite, which often forms the substrate for its crystals. ## Localities The only confirmed occurrence of rodolicoite in the world is the La Fossa crater on the volcanic island of Vulcano, part of the Aeolian Islands archipelago in Italy.

Rarity

Extremely rare

For collectors

## Quality Criteria For such a rare mineral, the only criterion is its confirmed presence on the sample. "Quality" specimens are those that contain well-formed, though still microscopic, crystal aggregates, identifiable and photographable under a microscope. The presence on a hematite-rich matrix can enhance aesthetic appeal. ## Popular Localities The only source of specimens is the type locality – the fumaroles of the La Fossa crater on Vulcano, Italy.

Care and storage

## Cleaning Due to its extreme rarity, small size, and fragility, rodolicoite specimens should not be cleaned mechanically or chemically. Any impurities should be left undisturbed. ## What to Avoid Avoid contact with any chemicals, ultrasonic cleaners, and sudden temperature changes. The mineral is susceptible to mechanical damage. ## Storage Specimens should be stored exclusively in specialized, sealed "micromount" boxes, protecting them from dust, vibrations, and humidity. Store under stable room conditions.

Sources

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