Huizingite-(Al)

Chemical formula: (N³⁻H₄)₉Al₃(S⁶⁺O₄)₈](OH)₂·4H₂O

Huizingite-(Al) is an extremely rare, water-soluble aluminum ammonium sulfate, forming microscopic, colorless crystals.

## Characteristics Huizingite-(Al) is a hydrated aluminum ammonium sulfate. It forms very small, platy or acicular crystals, usually not exceeding 200 micrometers in size. They are colorless and transparent. Due to its nature and small size, it is a mineral of interest mainly to specialized collectors and scientists. ## Physical Properties Huizingite-(Al) crystals exhibit a vitreous luster. This mineral is very soft and brittle. Its most characteristic feature is its complete solubility in water at room temperature. ## History and Name The mineral's name honors American mineralogist and curator Abraham "Abe" Huizinga Jr. (1933-2017) for his contributions to mineralogy. The "(Al)" suffix in the name indicates the dominance of aluminum in a specific position within the crystal structure. The mineral was approved by the IMA in 2011 (IMA2011-005).

Properties

Mohs hardness
2.5
Color
light greenish-yellow
Luster
Vitreous
Streak
white
Density
2.026
Cleavage
Perfect on {010}
Fracture
Irregular/Uneven
Transparency
Transparent
Crystal system
Triclinic

Diagnostic features

## Identification In practice, the identification of huizingite-(Al) relies on its occurrence environment (burning mine dumps) and co-occurring minerals. A key diagnostic feature is its complete solubility in water. However, confirming its identity requires advanced analytical methods, such as Raman spectroscopy or X-ray diffraction (XRD), due to the microscopic size of the crystals. ## Distinguishing from Similar Minerals It can be confused with other secondary sulfates formed under similar conditions, such as tschermigite, boussingaultite, or mascagnite. Huizingite-(Al) is distinguished from them by its specific chemical composition (presence of aluminum) and unique crystal structure, which can only be verified by laboratory methods. ## Crystal Forms It forms microscopic, elongated crystals with an acicular or thin-platy habit. They occur as single, dispersed crystals or small, loose aggregates on the surface of the host rock.

Geological environment

## Genesis Huizingite-(Al) is an anthropogenic mineral. It forms as a result of fumarolic processes on burning coal mine dumps. It is formed by sublimation from volcanic gases at temperatures ranging from 50 to 150°C, under low-pressure conditions. It crystallizes directly from the gas phase on the surface of shales or other rocks on the dump. ## Mineral Associations It co-occurs with other fumarolic minerals, such as native sulfur, sal ammoniac, mascagnite, tschermigite, and boussingaultite. ## Localities The only known occurrence of this mineral (type locality) is the burning coal mine dump of "Marcel" in Radlin, Upper Silesia, Poland.

Rarity

Extremely rare

For collectors

## Quality Criteria Due to its extreme rarity and microscopic size, every analytically confirmed specimen of huizingite-(Al) is scientifically and collector-wise valuable. Specimens with the largest possible, well-formed crystals, clearly visible against the host rock, are most highly prized. Precise documentation and confirmation of the mineral's identity are crucial.

Care and storage

## Cleaning The mineral **must not be cleaned** using any liquids, including water, alcohol, or ultrasonics. Any contact with water or moisture will cause its immediate and complete dissolution. ## What to Avoid Contact with water, water vapor, and high air humidity must be strictly avoided. It should be protected from all chemicals. It is very brittle, so shocks and mechanical pressure should be avoided. ## Storage Huizingite-(Al) specimens must be stored in hermetically sealed containers, preferably with a desiccant (e.g., silica gel). They should be kept at a stable room temperature, away from sources of heat and moisture.

External references

Sources

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