Adranosite

Chemical formula: (N<sup>3-</sup>H<sub>4</sub>)<sub>4</sub>NaAl<sub>2</sub>(S<sup>6+</sup>O<sub>4</sub>)<sub>4</sub>Cl(OH)<sub>2</sub>

Adranoite is a very rare sulfate, forming colorless, acicular crystals in volcanic environments.

## Characteristics Adranoite is a complex hydrated sulfate of sodium, aluminum, and ammonium. It occurs as small, prismatic or acicular crystals, rarely exceeding 1 mm in length. The crystals are typically colorless and transparent, with a vitreous luster. They most often form small, radial or tangled aggregates, growing on volcanic rocks. ## Physical Properties This mineral is very brittle and light, with a calculated density of approximately 2.45 g/cm³. Its Mohs hardness has not yet been determined due to the small size and fragility of the crystals. It is transparent and has a white streak. ## Colors and Varieties Typical adranoite is colorless. Its iron-rich variety, adranoite-(Fe), is known, in which aluminum is replaced by iron. It has similar physical properties but may exhibit a pale yellow or greenish tint. ## History and Name The mineral was first described in 2015 by a team of mineralogists led by Francesco Demartin. Its name comes from the city of Adrano, located near Mount Etna in Sicily, referring to the mineral's volcanic origin. However, the type locality is the La Fossa crater on Vulcano Island. ## Uses Adranoite has no industrial applications. Due to its rarity, fragility, and specific formation conditions, it is solely an object of scientific and collecting interest, mainly in the form of microminerals.

Properties

Luster
Vitreous
Streak
White
Density
2.45
Transparency
Transparent
Crystal system
Tetragonal

Diagnostic features

## Identification The key diagnostic feature of adranoite is its occurrence environment – active volcanic fumaroles. Identification is based on observing the crystal habit (small, acicular, colorless) and associated minerals. Final identification is only possible using advanced analytical methods, such as X-ray diffraction (XRD) or chemical microanalysis (EDS). ## Distinguishing from Similar Minerals Adranoite can be confused with other volcanic sublimation products, such as salammoniac (ammonium chloride) or mascagnite. Salammoniac usually forms dendritic or feathery coatings, while mascagnite has a different chemical composition and a slightly different crystal form. Precise differentiation in field conditions is practically impossible. ## Crystal Forms Adranoite crystals have a prismatic to acicular habit and crystallize in the tetragonal system. They typically occur as single, elongated needles or form radial, tangled, and sheaf-like aggregates.

Geological environment

## Genesis Adranoite is a mineral of volcanic origin. It forms through sublimation, crystallizing directly from hot volcanic gases (exhalations). It forms in fumaroles at temperatures of approximately 200-250°C, where gases rich in sulfur, ammonia, and other compounds react with rock components. ## Mineral Associations This mineral occurs in association with other volcanic sublimates. It most commonly co-occurs with salammoniac, mascagnite, and alunite. Its iron analog, adranoite-(Fe), is found in association with hematite. ## Localities Adranoite is an extremely rare mineral, and its occurrence has been confirmed in only a few places worldwide. The type locality and main source of specimens is the La Fossa crater on Vulcano Island (Aeolian Islands) in Italy.

Rarity

Very rare

For collectors

## Quality Criteria The quality of adranoite specimens, which occur exclusively as microminerals, is assessed based on several criteria. The most important is the sharpness and development of the crystals – specimens with distinct, undamaged needles are sought after. Aesthetic, radial aggregates on a contrasting substrate (matrix) are highly valued. The purity (lack of impurities) and transparency of the crystals also increase their collectible value. ## Popular Localities The only source for obtaining collectible specimens is the type locality – the La Fossa crater on Vulcano Island in Italy. All specimens available on the market come from this single location.

Care and storage

## Cleaning Adranoite specimens are extremely delicate and sensitive to moisture. They should absolutely not be cleaned with water or any liquids. The only safe method for removing dust is to very gently use a photographic air blower or a can of compressed air from a distance. ## What to Avoid Avoid contact with water and high humidity, which can lead to dissolution or damage to the crystals. The mineral is sensitive to temperature changes and mechanical shocks. Do not touch it with your fingers. ## Storage Adranoite must be stored in a dry place, preferably in an airtight container (e.g., a "micromount" box) away from vibrations and direct sunlight. Storage under stable temperature conditions is recommended.

External references

Sources

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