Maurogemmiite

Chemical formula: Ti₁₀Fe₃O₃

Maurogemmiite is an extremely rare titanium and iron oxide, forming microscopic, black, metallic crystals in volcanic fumaroles.

## Characteristics Maurogemmiite is a titanium and iron oxide, occurring as very small, tabular or platy crystals with a hexagonal outline. It typically forms rosette-like or irregular aggregates. Its crystals are black, opaque, and characterized by a strong metallic luster. Due to their microscopic size, specimens are mainly visible under magnification. ## Physical Properties The mineral's hardness is estimated at approximately 6.5 on the Mohs scale. It has a metallic luster and is opaque. The density calculated based on chemical composition and unit cell parameters is 4.65 g/cm³. ## Colors and Varieties It occurs exclusively in black. No color varieties or commercial varieties are known. ## History and Name The mineral was approved by the IMA in 2022. Its name honors Francesco Mauro (born 1962), an Italian mineral collector and specialist in Vesuvius minerals, for his contributions to mineralogy. The type locality is the La Fossa crater on Vulcano Island (Aeolian Islands), Italy.

Properties

Mohs hardness: 6.5
Luster: Metallic
Streak: Black
Density: 4.65
Cleavage: None
Transparency: Opaque
Crystal system: Trigonal

Diagnostic features

## Identification Identification of maurogemmiite based on visual characteristics is practically impossible due to its microscopic size and similarity to other black oxide minerals. The key is the environment of occurrence – high-temperature volcanic fumaroles. Definitive identification requires advanced analytical methods such as X-ray diffraction (XRD) and chemical microanalysis (EDS). ## Distinguishing from Similar Minerals It can be confused with hematite, ilmenite, rutile, pseudobrookite, and other iron and titanium oxides found in similar environments. Differentiation relies on analysis of chemical composition and crystal structure. ## Crystal Forms It forms thin, tabular crystals with a hexagonal outline, often grouped into rosette-like or chaotic aggregates.

Geological environment

## Genesis It forms through the process of sublimation from volcanic gases in high-temperature (above 600°C) exhalative fumaroles. ## Mineral Associations It co-occurs with other fumarolic minerals such as hematite, pseudobrookite, rutile, shcherbinaite, and baddeleyite. ## Localities The only confirmed locality in the world is its type locality – La Fossa crater on Vulcano Island, Sicily, Italy.

Rarity

Extremely rare

For collectors

## Quality Criteria For such a rare micromineral, the collector's value is primarily determined by the quality and development of the crystals – their sharpness, luster, and size. Rich crystal aggregates and aesthetic associations with other rare fumarolic minerals on a well-defined rock matrix are highly prized. ## Popular Localities The only source of specimens is the type locality on Vulcano Island, Italy.

Care and storage

## Cleaning Maurogemmiite specimens are extremely small and delicate. They should only be cleaned using compressed air from a safe distance or a very soft brush. Avoid contact with water and any chemicals. ## What to Avoid Do not use ultrasonic cleaners or chemical cleaning. The mineral should be protected from high temperatures, extreme changes in conditions, and direct contact with other chemicals that could damage the delicate crystals or host rock. ## Storage The safest way to store specimens is in a sealed "micromount" box, which protects the specimen from dust, shocks, and mechanical damage.

Sources

IMA Mineral List (CNMNC)