Aerinite

Chemical formula: (Ca,Na)<sub>6</sub>(Fe<sup>3+</sup>,Fe<sup>2+</sup>,Mg,Al)<sub>4</sub>(Al,Mg)<sub>6</sub>Si<sub>12</sub>O<sub>36</sub>(OH)<sub>12</sub>(CO<sub>3</sub>)·12H<sub>2</sub>O

Aerinite is a silicate mineral, valued for its characteristic, intense blue coloration and fibrous habit.

## Characteristics Aerinite is a complex silicate that visually presents as compact, massive, or fibrous aggregates with an intense blue color. It rarely forms visible crystals; its typical habit is massive fillings of fissures and vesicles in rocks. Its name perfectly reflects its characteristic sky-blue color. ## Physical Properties This mineral is relatively soft, with a Mohs hardness of approximately 3. It has a waxy luster, sometimes transitioning to dull, and its transparency ranges from translucent to completely opaque, depending on the thickness and compactness of the aggregate. Its density is approximately 2.48 g/cm³. ## Colors and Varieties Aerinite occurs almost exclusively in shades of blue – from light blue to dark, almost navy. The intensity and uniformity of the color are the main factors influencing its attractiveness. There are no distinct commercial or colored varieties. ## History and Name The name aerinite comes from the Greek word "aerinos" (ἀερινός), meaning "airy" or "sky-blue," which is a direct reference to its color. The mineral was first described in the 19th century, and its name was given by the German mineralogist Arnold von Lasaulx in 1876. ## Uses Due to its rarity and specific occurrence conditions, aerinite has no industrial applications. However, it is a valued and sought-after collector's stone, mainly because of its unique and vibrant color.

Properties

Mohs hardness
3
Luster
Waxy
Streak
Light blue
Density
2.47 - 2.51
Cleavage
None
Fracture
Uneven
Transparency
Translucent to opaque
Crystal system
Trigonal

Diagnostic features

## Identification The most important diagnostic feature of aerinite is its intensely blue color combined with low hardness (approximately 3 on the Mohs scale) and fibrous or compact structure. Its light blue streak is also characteristic. It occurs in a specific geological environment – in altered basic rocks. ## Distinguishing from Similar Minerals Aerinite is sometimes confused with other blue minerals: - **Azurite**: It is harder (3.5-4) and reacts vigorously with hydrochloric acid, effervescing. Aerinite does not exhibit such a reaction. - **Lazulite**: It is significantly harder (5-5.5). - **Chrysocolla**: Usually has a more greenish hue and often occurs in botryoidal or mammillary forms. ## Crystal Forms Aerinite most often forms microcrystalline, fibrous aggregates that fill fissures and voids in the host rock. It can occur as coatings, veins, or compact, massive forms. Well-formed crystals are extremely rare and appear as needles.

Geological environment

## Genesis Aerinite is a secondary mineral, forming under conditions of low-temperature metamorphism or hydrothermal processes. It forms as a result of the alteration of basic igneous rocks, such as basalts, andesites, or dolerites. It fills veins, fissures, and gas vesicles within them. ## Mineral Associations It often co-occurs with minerals such as prehnite, scolecite, calcite, and also with iron sulfides – pyrite and marcasite. ## Localities The most important and well-known aerinite localities worldwide are in Spain, in the Aragonese Pyrenees (Huesca province, e.g., near Estopiñán del Castillo) and in Andalusia. It is also known from occurrences in France (Saint-Pandelon).

Rarity

Not very common

For collectors

## Quality Criteria The most highly valued aerinite specimens are characterized by a deep, uniform, saturated blue color. The size and form of the aggregate are also important – thick veins of the mineral cutting through the host rock or massive fragments with a pure color are attractive. The contrast with white host rock or co-occurring minerals (e.g., white scolecite) enhances the visual appeal of the specimen. ## Popular Localities The localities in Spain, especially in the municipality of Estopiñán del Castillo in Huesca province, are considered classic and yield the best quality specimens. Specimens from this region are the benchmark for aerinite and command the highest prices in the collector's market.

Care and storage

## Cleaning Aerinite specimens should be cleaned very carefully due to their low hardness. It is best to use a soft brush to remove dust. If necessary, it can be rinsed with distilled water and then thoroughly dried with a soft cloth. ## What to Avoid Aerinite is susceptible to scratches, so contact with harder minerals should be avoided. It should be protected from acids and strong chemicals. Ultrasonic cleaners and steam cleaners are not recommended. ## Storage It is recommended to store aerinite specimens in separate, padded boxes or display cases to prevent abrasions and mechanical damage. It should be protected from dust and direct, prolonged exposure to sunlight, although it is not particularly sensitive to fading.

External references

Sources

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