Ammoniozippeite
Chemical formula: (N<sup>3-</sup>H<sub>4</sub>)<sub>2</sub>[(U<sup>6+</sup>O<sub>2</sub>)<sub>2</sub>(S<sup>6+</sup>O<sub>4</sub>)O<sub>2</sub>]·H<sub>2</sub>O
Ammoniozippeite is a rare, secondary uranium mineral of the zippeite group, forming yellow, earthy coatings and exhibiting strong fluorescence under UV light.
Description
## Characteristics Ammoniozippeite is a mineral of the zippeite group, belonging to the sulfate class. It occurs as fine-grained, earthy or powdery coatings and crusts on rocks. It rarely forms microscopic crystals with a platy habit. Its aggregates are soft and brittle. As a secondary uranium mineral, it is highly radioactive. ## Physical Properties Due to its mode of occurrence, hardness is difficult to determine precisely, but it is a very soft mineral. Luster is usually dull or earthy, and in the case of microcrystals, it can be vitreous. It is opaque in aggregates, and individual, microscopic crystals can be translucent. It exhibits strong, yellowish-green fluorescence under ultraviolet light (both short- and long-wave). ## Colors and Varieties Ammoniozippeite ranges in color from yellow, through golden-yellow to orange-yellow. No color or commercial varieties are distinguished. ## History and Name The mineral was first described in 1988 by J. Čejka, A. Muck, and F. Nováček. Its name refers to its chemical composition – the presence of ammonium ions (ammonio-) and its structural and chemical similarity to zippeite. The type locality is the Svornost uranium mine in Jáchymov, Czech Republic. ## Uses Ammoniozippeite has no industrial application. It is solely an object of scientific and collecting interest.
Diagnostic features
## Identification The most important diagnostic feature of ammoniozippeite is its intense yellowish-green fluorescence under UV light. In daylight, it is recognized by its yellow color, earthy or powdery form of occurrence, and co-occurrence with other secondary uranium minerals. Final identification is possible with a radiation detector (Geiger counter) and chemical analyses. ## Distinguishing from Similar Minerals Ammoniozippeite is visually indistinguishable from other minerals of the zippeite group, such as zippeite or natrozippeite. All form similar yellow, fluorescent coatings. It can also be confused with other secondary uranium minerals such as uranophane, carnotite, or tyuyamunite. Definitive differentiation requires advanced analytical methods, such as X-ray diffraction (XRD) or chemical microanalysis (EDS) to confirm the presence of ammonium ions. ## Crystal Forms It most often occurs as earthy, dusty, and loose coatings and crusts. Microscopic crystals in the form of thin lamellae or needles forming radial aggregates are very rarely observed.
Geological environment
## Genesis Ammoniozippeite is a secondary mineral, forming in the oxidation zones of uranium deposits. It forms as a result of the weathering of primary uranium minerals, mainly uraninite, under the influence of waters rich in sulfates and ammonium ions. It is often a contemporary (post-mining) product forming on the walls of old mine workings, where ammonium ions can originate from the decomposition of explosives used during mining operations. ## Mineral Associations It most often co-occurs with other secondary uranyl sulfates, such as zippeite, uranopilite, johannite, as well as with gypsum and other products of rock weathering. ## Localities The most important occurrences of this mineral are in the Czech Republic (Jáchymov - type locality) and in the United States, mainly on the Colorado Plateau in Utah (e.g., Delta, Lucky Boy, Freedom No. 2 mines).
Rarity
Rare
Collector aspects
## Quality Criteria The collector's appeal of ammoniozippeite specimens depends on several factors. Specimens with a large surface area covered by the mineral, intense, bright yellow color, and strong fluorescence are most valued. Rich associations with other rare uranium minerals are also highly regarded. Due to the microscopic nature of the crystals, specimens with visible (under magnification) crystalline aggregates are rarer and more desirable than typical earthy coatings. ## Popular Localities The most classic and valued specimens come from the historical locality in Jáchymov, Czech Republic. Specimens from mines in San Juan County, Utah, USA, which are famous for their rich and colorful coatings of secondary uranium minerals, are also often found on the collector's market.
Care and storage
## Cleaning Ammoniozippeite specimens are extremely delicate and potentially water-soluble. Cleaning should be kept to an absolute minimum. Only very careful removal of loose dust with a soft brush is permissible. Any contact with water and other liquids should be avoided. ## What to Avoid The mineral is highly radioactive. Inhalation of dust and direct skin contact should be avoided. Hands should be thoroughly washed after any contact with the specimen. It must not be heated or exposed to acids. It is sensitive to moisture. ## Storage Due to radioactivity, specimens should be stored in sealed, lead-lined or thick-walled plastic containers, clearly marked with the radioactivity symbol. They should be kept away from other minerals (to avoid their activation), and also away from areas of permanent human presence, in a well-ventilated room.