Cortesognoite

Chemical formula: CaV<sup>3+</sup><sub>2</sub>Si<sub>2</sub>O<sub>7</sub>(OH)<sub>2</sub>·H<sub>2</sub>O

Cortesognoite is a very rare, green vanadium silicate from the sorosilicate group, forming microscopic, radial aggregates.

## Characteristics Cortesognoite is a hydrated calcium vanadium silicate, belonging to the rare minerals of the epidote group. It occurs as very small, acicular or bladed crystals, which most often form radial or fibrous aggregates. Due to the microscopic size of the crystals, its visual features are difficult to observe without magnification. Individual crystals are usually too small to be analyzed with the naked eye. ## Physical Properties Cortesognoite crystals exhibit a vitreous luster. Its Mohs hardness is approximately 6. It is a relatively dense mineral, and its density, calculated based on the chemical formula and unit cell parameters, is 3.43 g/cm³. ## Colors and Varieties This mineral is characterized by a vivid green color with a yellowish tint. No color varieties or commercial varieties are known. ## History and Name Cortesognoite was discovered in the Valgraveglia rodingite mine in Liguria, Italy. It was described and approved as a new mineral by the International Mineralogical Association (IMA) in 1997. Its name honors Professor Germano Cortesogno (born 1940), an Italian petrologist from the University of Genoa, for his contributions to the study of metamorphic rocks in Liguria. ## Uses Cortesognoite has no industrial applications. Its significance is purely scientific and collectible, as a very rare representative of vanadium silicates.

Properties

Mohs hardness
6
Luster
Vitreous
Streak
Light green
Density
3.43
Cleavage
Good on {001}
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of cortesognoite is possible almost exclusively using advanced laboratory methods, such as X-ray diffraction (XRD) and chemical microanalysis (EDS/WDS). In collector conditions, identification is based on its green color, radial habit of aggregates, and, most importantly, its confirmed occurrence locality (Valgraveglia mine). ## Distinguishing from similar minerals It can be confused with other green vanadium silicates, such as natalynite or suolunite, with which it co-occurs. Distinguishing it from these requires specialized chemical and crystallographic analysis. Visually, it is practically indistinguishable from these minerals. ## Crystal Forms It forms very fine, acicular or bladed crystals up to 0.1 mm long. These crystals arrange themselves into characteristic, radial or fibrous aggregates, as well as rosette-like clusters.

Geological environment

## Genesis Cortesognoite forms under specific conditions within rodingites – metasomatic rocks rich in calcium and silicon, which are formed as a result of the serpentinization of ophiolites. It is a product of hydrothermal processes or low-grade metamorphism occurring in a vanadium-rich environment. ## Mineral Associations This mineral occurs in association with other rare vanadium minerals, such as natalynite, suolunite, and vanadiocarfolite. It also co-occurs with diopside, titanite, chlorite, vesuvianite, and garnets (andradite). ## Localities The only confirmed and described locality of cortesognoite in the world is its type locality – the Valgraveglia rodingite mine, located in the municipality of Ne, in the Liguria region of Italy.

Rarity

Extremely rare

For collectors

## Quality Criteria As a "micromount" mineral, the value of a specimen is primarily determined by the richness and development of crystal aggregates on the rock matrix. The most prized samples are those with distinct, radial clusters of intense green color, contrasting well with the host rock. Association with other rare vanadium minerals is also important. ## Popular Localities The only source of collector specimens is the Valgraveglia mine in Italy. All samples available on the market originate from this single locality.

Care and storage

## Cleaning Cortesognoite specimens, due to their microscopic nature and delicacy, should be cleaned with the utmost care. It is safest to use compressed air to remove dust. Any contact with water or chemicals is inadvisable without specialized knowledge. ## What to avoid Avoid contact with acids and other chemicals that may damage the mineral. Ultrasonic cleaning and mechanical cleaning (e.g., with brushes) are also inadvisable, as they could destroy the tiny, acicular crystals. Store away from heat sources. ## Storage Specimens should be stored in stable conditions, preferably in sealed "micromount" boxes, which protect against dust, mechanical damage, and sudden changes in humidity. Exposure to strong light is not recommended, although there is no evidence of fading.

Sources

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