Davidbrownite-(NH_4_)

Chemical formula: (N<sup>3-</sup>H<sub>4</sub>)<sub>5</sub>(V<sup>4+</sup>O)<sub>2</sub>((C<sub>2</sub>)<sup>6+</sup>O<sub>4</sub>)[PO<sub>2.75</sub>(OH)<sub>1.25</sub>]<sub>4</sub>·3H<sub>2</sub>O

Davidbrownite-(NH₄) is an extremely rare mineral from the phosphate group, discovered in a uranium mine in Utah, USA.

## Characteristics Davidbrownite-(NH₄) is a mineral with an exceptionally complex chemical composition, containing ammonium, vanadium, oxalate, and phosphate groups. It occurs as very small, tabular crystals, not exceeding 0.2 mm in size, forming aggregates and coatings. Its uniqueness lies in the coexistence of ammonium and oxalate ions in its structure, which is a rarity in the mineral world. ## Physical Properties The crystals are too small to precisely determine standard physical properties such as hardness or density. The mineral exhibits a vitreous luster and is transparent. Due to the small size of the crystals, most characteristics are observed under a microscope. ## Colors and Varieties Davidbrownite-(NH₄) is characterized by a pale blue color. No varieties are known. ## History and Name The mineral was officially recognized by the International Mineralogical Association (IMA) in 2016 under number IMA2016-053. Its name honors David Brown, a renowned mineral collector from Utah, who found the first samples. The suffix "-(NH₄)" refers to the dominant ammonium ion in its chemical structure. ## Applications Davidbrownite-(NH₄) has no industrial applications. It is of interest solely for scientific and collecting purposes due to its extreme rarity and unique chemical composition.

Properties

Luster
Vitreous
Transparency
Transparent
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of the mineral is possible only through advanced analytical methods, such as Raman spectroscopy or X-ray diffraction (XRD), due to its microscopic size and rarity. Field identification or identification in a typical collection is impossible. Its characteristic pale blue color and occurrence in association with other rare uranyl minerals may be an indication. ## Distinguishing from Similar Minerals It may be confused with other secondary, pale blue uranyl minerals. Definitive differentiation requires specialized chemical and structural analysis. ## Crystal Forms It forms very small, thin, tabular crystals, which often arrange into rosette-like or spherical aggregates.

Geological environment

## Genesis Davidbrownite-(NH₄) is a secondary mineral that formed in the oxidation zone of a uranium deposit. Its genesis is associated with the weathering processes of primary minerals in the presence of organic matter (e.g., fossilized wood), which was the source of oxalate groups, and ammonia-rich solutions. ## Mineral Associations This mineral co-occurs with other rare secondary uranium minerals, such as gypsum, quartz, pyrite, montroseite, as well as other uranyl oxalates and phosphates. ## Localities The only confirmed occurrence worldwide (type locality) is the Markey uranium mine in San Juan County, Utah, USA.

Rarity

Extremely rare

For collectors

## Quality Criteria Due to its extreme rarity, every specimen of davidbrownite-(NH₄) is valuable. The value is primarily determined by the abundance and size of crystalline aggregates on the rock matrix and the aesthetic composition with associated minerals. Even microscopic but well-formed crystals are highly prized. ## Popular Localities The only source of specimens is the Markey mine in Utah, USA. Material from this locality is highly sought after by specialized collectors of rare minerals and micromounts.

Care and storage

## Cleaning Due to the extreme delicacy and small size of the crystals, mechanical or chemical cleaning is absolutely inadvisable. Specimens should be left in their undisturbed state. ## What to Avoid Avoid contact with water, chemicals, ultrasound, and any vibrations or shocks. The mineral is likely sensitive to changes in temperature and humidity. It should not be exposed to direct sunlight. ## Storage Specimens should be stored exclusively in specialized, sealed "micromount" boxes, protecting them from dust, humidity, and mechanical damage. Storage in stable room conditions is crucial for preserving the integrity of the sample.

Sources

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