Fernandinite

Chemical formula: (Ca,Na,K)₀.₉(V⁵⁺,V⁴⁺,Fe²⁺,Ti⁴⁺)₈O₂₀·4H₂O

Fernandinite is a rare, hydrated vanadium oxide with a characteristic dull green color, forming fibrous and earthy aggregates.

## Characteristics Fernandinite is a mineral from the straczekite group, chemically classified as a hydrated vanadium oxide with calcium, sodium, and potassium. It most commonly occurs as earthy aggregates, masses filling rock fractures, or as fibrous and radial aggregates. It rarely forms discernible crystals. Its appearance is usually dull and inconspicuous, resembling coatings or compact masses. ## Physical Properties This mineral is relatively soft, with a Mohs hardness of 2-3, allowing it to be scratched by a copper wire. It has a density of approximately 2.78 g/cm³. It is translucent to opaque. The luster is described as dull or earthy. ## Colors and Varieties Fernandinite is characterized by various shades of green. It is most commonly found in a dull green color. In transmitted light, it can exhibit colors ranging from light green, through dark olive, to greenish-brown. No named varieties are distinguished. ## History and Name The mineral was first described in 1915. Its name comes from Eulogio Fernando, a Peruvian geologist and director of the Ragra mine in Peru, which is its type locality. It was there that this mineral was discovered. ## Uses Due to its rarity and inconspicuous appearance, fernandinite has no industrial applications. It is solely an object of interest for collectors specializing in rare vanadium minerals and minerals from specific localities.

Properties

Mohs hardness
2-3
Luster
Dull
Streak
Dark green
Density
2.78
Cleavage
None
Fracture
Sub-Conchoidal,Micaceous
Transparency
Translucent,Opaque
Crystal system
Monoclinic

Diagnostic features

## Identification Fernandinite is recognized by its characteristic dull green color, low hardness (2-3 on the Mohs scale), and occurrence in the form of earthy, fibrous, or radial aggregates. A dark green streak is also an important diagnostic feature. It usually occurs as an oxidation product of other vanadium minerals. ## Distinguishing from Similar Minerals It can be confused with other secondary green vanadium minerals, such as hewettite, pascoite, or various "vanadium greens." Differentiation often requires chemical analysis (EDS) or X-ray diffraction (XRD). It differs from hewettite by the presence of calcium, and from pascoite, which is orange-red, by its color. ## Crystal Forms Well-formed crystals are practically nonexistent. The mineral forms fibrous, radial, spherulitic aggregates, as well as massive, compact, and earthy coatings and fillings in rocks.

Geological environment

## Genesis Fernandinite is a secondary mineral, formed in the oxidation (weathering) zone of vanadium deposits. It forms as a result of the alteration of primary vanadium minerals, such as patronite (vanadium sulfide), under conditions of low temperatures and pressures, with access to oxygen and water. ## Mineral Associations This mineral co-occurs with other vanadium minerals, especially those of a secondary nature. In its type locality (Ragra mine), it was found in association with hewettite, pascoite, minasragrite, as well as native sulfur and gypsum. ## Localities The most important and historical occurrence of fernandinite is its type locality - the Ragra mine in the Huayllay district, Pasco region, Peru. This is the only confirmed and significant locality for this mineral in the world.

Rarity

Very rare

For collectors

## Quality Criteria The collector appeal of fernandinite is low due to its inconspicuous appearance. The most valued specimens are those that show a distinct fibrous or radial structure, rather than just an earthy coating. Association with other, more aesthetic vanadium minerals is also important. The purity and intensity of the green color can slightly increase the value of a specimen. ## Popular Localities The only source of collector specimens is the historical type locality - the Ragra mine in Peru. Material from this location is extremely difficult to obtain, as the mine has not been exploited for mineral extraction for a long time.

Care and storage

## Cleaning Fernandinite specimens are very delicate and sensitive. They should only be cleaned with a soft brush or compressed air to remove dust. Any contact with water or other liquids is inadvisable, as it can lead to damage or disintegration of the aggregates. ## What to Avoid Water, chemicals, ultrasonic cleaners, and sudden temperature changes should be absolutely avoided. The mineral is soft and brittle, so it must be protected from impacts, scratching, and vibrations. It should not be exposed to direct sunlight, which can cause color changes. ## Storage It is recommended to store specimens in closed, padded collector boxes, away from dust, moisture, and light sources. It is best to keep it in stable temperature and humidity conditions, away from other, harder minerals that could damage it.

External references

Sources

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