Aluminopyracmonite

Chemical formula: (N₃-H₄)₃Al(S₆+O₄)₃

Aluminopyracmonite is an extremely rare ammonium-aluminum sulfate, forming colorless, microscopic crystals in volcanic fumaroles.

## Characteristics Aluminopyracmonite is an aluminum and ammonium sulfate with the chemical formula (NH₄)₃Al(SO₄)₃. It is the aluminum (Al) analog of pyracmonite, where aluminum replaces iron (Fe). It occurs as small, colorless to white, hexagonal crystals with a tabular or short prismatic habit. It typically forms fine coatings, crusts, and crystalline aggregates on rocks in the immediate vicinity of volcanic exhalations. ## Physical Properties Aluminopyracmonite crystals are characterized by a vitreous luster and are transparent to translucent. Due to the microscopic size and fragility of the crystals, its Mohs hardness has not been determined. The density calculated from the unit cell parameters is approximately 2.13 g/cm³. ## Colors and Varieties This mineral is colorless or white. No colored or commercial varieties have been identified. ## History and Name The name "aluminopyracmonite" refers to its chemical composition – the presence of aluminum – and its relationship to the structurally identical pyracmonite. The mineral name was approved by the International Mineralogical Association (IMA) in 2012. The name of the parent mineral, pyracmonite, comes from the Greek words *pyr* (fire) and *kmon* (anvil), an allusion to the mythological forge of Hephaestus (Vulcan), which was said to be located in the crater of the Vulcano volcano – the discovery site of both minerals. ## Applications Aluminopyracmonite, due to its extreme rarity and microscopic size, has no practical applications. It is solely an object of scientific interest and a collector's item for specialized mineral collectors (micromounters).

Properties

Luster: Vitreous
Streak: White
Density: 2.13
Transparency: Transparent to Translucent
Crystal system: Trigonal

Diagnostic features

## Identification Identification of aluminopyracmonite under amateur conditions is practically impossible. A key clue is its unique occurrence environment – high-temperature volcanic fumaroles. Under high magnification, characteristic, small hexagonal crystals can be observed. Definitive identification requires advanced analytical techniques, such as X-ray diffraction (XRD) or chemical microanalysis (EDS/WDS). ## Distinguishing from Similar Minerals Aluminopyracmonite is visually indistinguishable from pyracmonite ((NH₄)₃Fe(SO₄)₃) – differentiation requires chemical analysis to determine the dominance of aluminum over iron. It can also be confused with other white, crystalline volcanic sublimates, such as godovikovite or other ammonium sulfates. Mineralogical context and crystal form can be helpful but are not decisive. ## Crystal Forms It forms microscopic, hexagonal crystals, most often with a flattened, tabular habit. It occurs as crystalline coatings, thin crusts, and small aggregates on the surface of volcanic rocks.

Geological environment

## Genesis Aluminopyracmonite is a fumarolic mineral. It forms by direct sublimation from hot volcanic gases (exhalations) at temperatures ranging from 250 to 400°C. ## Mineral Associations It co-occurs with other fumarolic minerals, such as pyracmonite, godovikovite, alunogen, native sulfur, anhydrite, and alunite. ## Localities The only confirmed locality of aluminopyracmonite in the world is its type locality – the active La Fossa crater on Vulcano Island, part of the Aeolian Islands archipelago in Italy.

Rarity

Extremely rare

For collectors

## Quality Criteria As a mineral available only in the form of microscopic specimens (so-called micromounts), its collector's value depends on the richness of the crystalline coating on the rock matrix, the size and sharpness of the individual crystals, and the aesthetics of the entire composition. Specimens with clearly visible, single hexagonal crystals are most prized. ## Popular Localities All known collector specimens come from a single location in the world – the La Fossa crater on the Italian island of Vulcano. It is an extremely difficult mineral to acquire, available almost exclusively through specialized channels.

Care and storage

## Cleaning Aluminopyracmonite is an extremely delicate mineral and is water-soluble. Cleaning should only be done dry, using a very soft brush or carefully blowing off dust with a stream of compressed air from a safe distance. Any contact with water or other liquids will cause its destruction. ## What to Avoid Contact with water, water vapor, and high humidity must be strictly avoided, as the mineral is hygroscopic and easily dissolves. It should be protected from all chemicals, acids, and detergents. It is thermally unstable and should not be heated. ## Storage Aluminopyracmonite specimens must be stored in sealed, airtight containers (e.g., "perky boxes") with a desiccant (e.g., silica gel) to ensure a constant, dry environment. They should be kept in a dark place with a stable temperature, away from direct sunlight and heat sources.

Sources

IMA Mineral List (CNMNC)