Kummerite

Chemical formula: Mn<sup>2+</sup>Fe<sup>3+</sup>Al(PO<sub>4</sub>)<sub>2</sub>(OH)<sub>2</sub>·8H<sub>2</sub>O

Kummerite is a very rare, hydrated manganese, iron, and aluminum phosphate, forming microscopic, platy yellow crystals.

## Characteristics Kummerite is an extremely rare mineral from the phosphate group, chemically classified as a hydrated manganese, iron, and aluminum phosphate. It occurs as very small, platy or acicular crystals, rarely exceeding fractions of a millimeter in length. These crystals often form radial or tangled aggregates. Due to its microscopic size, it is a mineral of interest mainly to specialized collectors (micromounters). ## Physical Properties Kummerite crystals are characterized by a vitreous luster and are transparent. Hardness and density have not been precisely determined due to the small size of the samples; however, like most hydrated phosphates, it is a relatively soft mineral. It is brittle, and its crystals are flexible. ## Colors and Varieties This mineral occurs in a characteristic yellow color, sometimes with a brownish tint. No varieties have been distinguished. ## History and Name Kummerite was discovered in the dumps of the Hagendorf-Süd mine in Bavaria (Germany) and described as a new mineral in 1984 by Paul Keller and Pete J. Dunn. The name honors Rudolf Kummer, a German mineral collector who first found specimens of this mineral and brought them to the attention of researchers.

Properties

Luster
Vitreous
Streak
Light yellow
Cleavage
Good on {010}
Fracture
Uneven
Transparency
Transparent
Crystal system
Monoclinic

Diagnostic features

## Identification Identification of kummerite under amateur conditions is practically impossible. It requires specialized analytical methods, such as X-ray diffraction (XRD) and chemical microanalysis (EDS/WDS). Initial indications may include its form (fine, platy crystals in radial aggregates), yellow color, and co-occurrence with other rare phosphates in granitic pegmatites. ## Distinguishing from Similar Minerals Kummerite can be confused with many other secondary, yellow phosphate minerals found in pegmatites, such as Cacoxenite, Strunzite, or Beraunite. Definitive differentiation is only possible using advanced laboratory techniques. ## Crystal Forms Kummerite forms elongated, platy crystals with a rhombic cross-section, terminating acutely. Crystals are often flattened and exhibit striations along the elongation axis. They usually occur as radial or tangled aggregates.

Geological environment

## Genesis Kummerite is a secondary hydrothermal mineral, forming in the oxidation zones of phosphate deposits in granitic pegmatites. It forms as a result of the alteration of primary phosphate minerals, such as Zwieselilite, in the presence of aluminum-rich solutions. ## Mineral Associations This mineral co-occurs with other secondary phosphates. At its type locality (Hagendorf-Süd), it was found in association with Strunzite, Beraunite, Stewartite, Laueite, Rockbridgeite, Strengite, as well as Goethite and Quartz. ## Localities The only confirmed and well-documented occurrence of kummerite in the world is its type locality – the Hagendorf-Süd pegmatite in Waidhaus, Upper Palatinate, Bavaria (Germany).

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a kummerite specimen is assessed based on the richness and aesthetics of the microcrystal aggregates on the rock matrix. Specimens with clearly formed, radial groups of crystals of intense yellow color, contrasting with the substrate, are most valued. Due to the microscopic nature of the mineral, the quality of the specimen as seen under magnification is crucial. ## Popular Localities The only source of kummerite specimens is the Hagendorf-Süd mine in Germany. Material from this location is extremely rare and sought after by specialized micromineral collectors.

Care and storage

## Cleaning Kummerite specimens, typically microscopic crystals on a rock matrix, do not require cleaning. If absolutely necessary, compressed air can be used to remove dust. Avoid contact with water and any chemicals. ## What to Avoid Ultrasonic cleaners, chemical agents, acids, and high temperatures, which can cause dehydration and destruction of the mineral's structure, should be absolutely avoided. The crystals are very brittle and susceptible to mechanical damage. ## Storage Micromineral collections, such as kummerite, are best stored in special, sealed boxes (e.g., "micromount boxes") that protect delicate specimens from dust, moisture, and physical damage.

Sources

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