Nordgauite
Chemical formula: Mn<sup>2+</sup>Al<sub>2</sub>(PO<sub>4</sub>)<sub>2</sub>F<sub>2</sub>·5.5H<sub>2</sub>O
Nordgauite is a very rare, hydrated manganese aluminum fluorophosphate, forming colorless or white, platy crystals aggregated into rosettes.
Description
## Characteristics Nordgauite is a phosphate group mineral, chemically classified as a hydrated manganese aluminum fluorophosphate. It occurs as small, thin, platy or bladed crystals, almost always forming characteristic, radial or fan-shaped aggregates resembling rosettes. Individual crystals rarely exceed 1-2 mm in length. The mineral is most often colorless or white, sometimes with a delicate pink or yellowish tint. It exhibits a vitreous luster, which transitions to pearly on surfaces of perfect cleavage. ## Physical Properties The Mohs hardness of nordgauite is approximately 3, making it a relatively soft and easily scratched mineral. It is brittle, and its density is about 2.51 g/cm³. It exhibits excellent cleavage in one plane, which, combined with the thinness of the crystals, makes specimens very delicate. It is transparent to translucent. ## Colors and Varieties This mineral does not form colored commercial or gemological varieties. Its color palette is limited to shades of white, and it can also be completely colorless. The pale pink coloration is likely associated with the presence of manganese in its structure. ## History and Name Nordgauite was officially recognized as a new mineral species by the International Mineralogical Association (IMA) in 2014 (IMA 2014-080). Its name comes from the medieval region of Nordgau, which historically encompassed the area of today's Upper Palatinate (Oberpfalz) in Bavaria (Germany). The first specimens of this mineral were discovered in the Hagendorf-Süd pegmatite in this area. ## Applications Due to its extreme rarity and microscopic crystal sizes, nordgauite has no industrial applications. It is solely an object of scientific interest and a prized acquisition in advanced collections of rare and systematic minerals.
Diagnostic features
## Identification The most important diagnostic feature of nordgauite is its mode of occurrence – characteristic, rosette-like or fan-shaped aggregates composed of very thin, platy crystals. The pearly luster on cleavage planes and its occurrence in paragenesis with other rare phosphates in pegmatites are also key indicators. It is a soft mineral that does not scratch glass. ## Distinguishing from Similar Minerals Nordgauite can be confused with other white or colorless secondary minerals found in pegmatites. It differs from white micas (e.g., muscovite) by the lack of elasticity of its lamellae. From wavellite, which also forms radial aggregates, it differs in crystal form – wavellite forms acicular crystals in spherical aggregates, while nordgauite forms flat, platy crystals in flat rosettes. Final confirmation of identity almost always requires advanced analytical methods, such as EDS spectroscopy or X-ray diffraction (XRD). ## Crystal Forms Crystals are thin-platy, bladed, elongated, or lamellar. They always occur in complex aggregates: fan-shaped, radial, and most often in beautiful, rosette-like clusters.
Geological environment
## Genesis Nordgauite is a secondary mineral, formed in hydrothermal alteration zones within complex, phosphate-rich granitic pegmatites. It forms as a result of the circulation of solutions that interact with primary phosphate minerals, such as triphylite or zwieselite, leading to the precipitation of new, hydrated mineral phases in rock cavities and fissures. ## Mineral Associations This mineral co-occurs with other, often rare, secondary phosphates. In its type locality (Hagendorf-Süd), it has been found in association with scholzite, zwieselite, apatite, strengite, rockbridgeite, as well as pegmatite-forming minerals such as quartz and muscovite. ## Localities Nordgauite is a very rare mineral. The most important and historically first locality is the Hagendorf-Süd pegmatite in Waidhaus, in the Upper Palatinate, Bavaria (Germany). This is the source of the highest quality specimens. Beyond this locality, its presence has been reported in several other places worldwide with similar geology, but it remains a great rarity.
Rarity
Very rare
Collector aspects
## Quality Criteria The collector's value of nordgauite is primarily determined by its rarity. The most highly prized specimens are those with well-formed, sharp, and undamaged rosette aggregates. The size of the clusters is important – the larger and more distinct the rosette, the more valuable the specimen. A contrasting matrix, e.g., dark quartz, and the presence of other rare phosphate minerals significantly enhance the visual appeal and value of the specimen. ## Popular Localities The only commercially significant source of collector's specimens of nordgauite is its type locality: the Hagendorf-Süd pegmatite mine in Bavaria, Germany. Specimens from this location are considered the global standard for this mineral.
Care and storage
## Cleaning Nordgauite specimens are extremely delicate and must be handled with the utmost care. For dust removal, it is best to use a soft brush or a carefully directed stream of compressed air. Washing in water is not recommended; if absolutely necessary, use distilled water and immediately dry the specimen, avoiding any soaking. ## What to Avoid Ultrasonic cleaners should be absolutely avoided, as they would destroy the brittle crystals. The mineral is sensitive to acids and other strong chemicals. Due to the hydration in its structure, heating should be avoided, as it can lead to permanent damage. Protect from impacts and vibrations. ## Storage It is recommended to store nordgauite specimens in sealed "micromount" boxes, which protect them from dust, mechanical damage, and sudden changes in humidity. Display should be away from areas exposed to shocks or direct sunlight.