Ammoniolasalite

Chemical formula: (N₃-H₄)₂Mg₂[V₅+₁₀O₂₈]·₂₀H₂O

Ammoniolasalite is a very rare, water-soluble magnesium ammonium decavanadate, forming aggregates of microscopic, acicular crystals.

## Characteristics Ammoniolasalite is a hydrated magnesium ammonium decavanadate. It occurs as aggregates of very small, acicular or bladed crystals, rarely exceeding 0.2 mm in length. It forms stellate or radial aggregates, and also appears as coatings and efflorescences on rock surfaces. ## Physical Properties Ammoniolasalite crystals are extremely brittle and delicate. This mineral is water-soluble. Due to the microscopic size of the crystals, determining many physical properties, such as hardness or density, is difficult. ## Colors and Varieties Ammoniolasalite has a characteristic, pale yellow color. No color varieties or commercial varieties are known. ## History and Name The mineral was approved by the IMA in 2021. Its name refers to its chemical composition – the presence of ammonium ions (ammonio-) – and its structural and chemical similarity to the mineral lasalite. ## Applications Ammoniolasalite has no industrial applications. It is solely an object of scientific and collector interest due to its extreme rarity.

Properties

Luster: Vitreous
Streak: Light yellow
Cleavage: Perfect on {010}
Transparency: Transparent
Crystal system: Monoclinic

Diagnostic features

## Identification Key diagnostic features include its pale yellow color, acicular or bladed crystal habit forming stellate aggregates, and its occurrence as efflorescences on sandstones. Water solubility is a confirming feature, but testing it destroys the sample. ## Distinguishing from Similar Minerals Ammoniolasalite can be confused with other secondary vanadium minerals, such as carnotite or tyuyamunite, which also have a yellow color and occur as coatings. Differentiation requires advanced analytical methods, such as Raman spectroscopy or X-ray diffraction (XRD). It differs from lasalite, to which it is similar, by the presence of ammonium ions. ## Crystal Forms The mineral forms very fine, acicular or bladed crystals, usually grouped into radial or stellate aggregates. It also occurs as powdery coatings and efflorescences.

Geological environment

## Genesis Ammoniolasalite is a secondary mineral, formed as a result of weathering processes of sedimentary rocks containing vanadium. It forms as an evaporitic product of waters rich in vanadium, magnesium, and ammonium ions in an arid climate. Its presence is associated with uranium-vanadium sandstones. ## Mineral Associations This mineral co-occurs with other secondary vanadates. At the type locality (Burro Mine), it was found in association with gypsum, huemulite, lasalite, rossite, and metarossite. ## Localities The only confirmed locality of ammoniolasalite in the world is its type locality – the Burro Mine (formerly Williams Mine) in San Miguel County, Colorado, USA.

Rarity

Extremely rare

For collectors

## Quality Criteria Due to its extreme rarity and microscopic crystal size, every analytically confirmed specimen is valuable. The most desirable samples are those with clearly visible, rich aggregates of stellate crystals on a piece of matrix rock. A contrasting sandstone matrix enhances aesthetic appeal. ## Popular Localities The only source of specimens is the Burro Mine in Colorado, USA. Material from this locality is extremely difficult to obtain and appears on the collector's market sporadically.

Care and storage

## Cleaning The mineral is water-soluble, so it must absolutely not be cleaned wet. Contact with any liquid should be avoided. Specimens can only be cleaned using compressed air (from a safe distance) or a very soft brush, with the utmost care. ## What to Avoid Contact with water, alcohol, and other chemicals must be strictly avoided. The mineral is sensitive to atmospheric moisture, which can lead to its slow degradation. It should be protected from temperature changes and direct sunlight. ## Storage Ammoniolasalite specimens must be stored in sealed, airtight containers (e.g., "perky box" type) with a desiccant (silica gel). They should be displayed away from sources of vibration, heat, and light.

Sources

IMA Mineral List (CNMNC)