Thebaite-(NH_4_)

Chemical formula: (N₃-H₄)₃Al((C₂)₆+O₄)(PO₃OH)₂(H₂O)

Tebait-(NH₄) is an extremely rare, hydrated aluminum ammonium phosphate-oxalate, occurring as microscopic, colorless crystals in guano caves.

## Characteristics Tebait-(NH₄) is a mineral from the phosphate and oxalate group, characterized by a complex chemical composition. It forms extremely small, colorless, bladed or tabular crystals, reaching sizes up to 200 micrometers. They usually occur as single, dispersed crystals or small aggregates. Due to its microscopic size, its visual features are not discernible to the naked eye and require significant magnification for observation. ## Physical Properties Tebait-(NH₄) crystals exhibit a vitreous luster. They are transparent and colorless. The hardness and density of the mineral have not been precisely determined due to the small amount of available material and the microscopic size of the crystals. ## History and Name The mineral's name comes from the Tebaida (Thèbes) cave in Egypt, which is its type locality. The -(NH₄) suffix in the name indicates the dominant ammonium cation in its structure. The mineral was approved by the International Mineralogical Association (IMA) in 2022 under number IMA2022-075. It was described by an international team of researchers, including Anthony R. Kampf, Stuart J. Mills, Chi Ma, and Fabrice Dal Bo.

Properties

Luster: Vitreous
Streak: White
Cleavage: Perfect on {010}
Fracture: Uneven
Transparency: Transparent
Crystal system: Monoclinic

Diagnostic features

## Identification Identification of tebait-(NH₄) is possible only through advanced analytical methods, such as single-crystal X-ray diffraction (SC-XRD) and energy-dispersive X-ray spectroscopy (EDS). It is unrecognizable and indistinguishable from many other microminerals with the naked eye or under a standard microscope. ## Distinction from Similar Minerals Based on visual characteristics alone, it is impossible to distinguish it from other colorless, microscopic secondary minerals found in cave deposits, such as taranakite, brushite, or other phosphates. Definitive distinction requires specialized chemical and structural analysis. ## Crystal Forms The mineral forms very small, elongated crystals with a bladed or tabular habit, flattened parallel to {010}.

Geological environment

## Genesis Tebait-(NH₄) is a secondary mineral. It forms in a specific cave environment as a result of reactions between solutions percolating through bat guano deposits and clay minerals (containing aluminum) originating from the surrounding rocks. ## Mineral Associations At the type locality, tebait-(NH₄) is associated with guanoxalate, taranakite, brushite, newberyite, aphthitalite, halite, sylvite, and gypsum. ## Localities The only confirmed occurrence of tebait-(NH₄) in the world is the Tebaida (Thèbes) cave, located near ancient Thebes (modern Luxor) in Upper Egypt.

Rarity

Extremely rare

For collectors

## Quality Criteria As an extremely rare micromount mineral, any analytically confirmed specimen is considered exceptionally valuable. The most highly prized specimens would be those with the largest possible (though still microscopic), well-formed, and isolated crystals, set on a contrasting rock matrix. Due to the nature of the mineral, clarity and color are not key criteria. ## Popular Localities The only source of specimens is the type locality – the Tebaida cave in Egypt. Material from this location is practically unavailable on the collector's market and is mainly found in scientific institutions.

Care and storage

## Cleaning Due to its extreme rarity, microscopic size, and delicacy, tebait-(NH₄) specimens should not be subjected to any standard cleaning procedures. Any manipulation should be kept to an absolute minimum and performed only under laboratory conditions by specialists. ## What to Avoid Contact with water, chemicals, ultrasound, and any mechanical stress should be avoided. The mineral is likely sensitive to changes in humidity and temperature. It should not be exposed to direct sunlight. ## Storage Specimens should be stored under stable conditions, preferably in their original micromount container, protected from dust, shocks, and humidity changes. Store in a dark and dry place.