Fluckite

Chemical formula: CaMn²⁺(As⁵⁺O₃OH)₂·₂H₂O

Fluckite is a rare, hydrated calcium manganese arsenate, forming tiny, pink or colorless crystals with a vitreous luster.

## Characteristics Fluckite is a hydrated calcium manganese arsenate belonging to the picropharmacolite group. It occurs as very small, bladed or acicular crystals, rarely exceeding 1 mm in length. These crystals often form radial or disordered aggregates, as well as coatings and efflorescences on rocks. Due to its small size, its visual features are difficult to observe without magnification. ## Physical Properties Fluckite crystals are characterized by a vitreous luster and are transparent to translucent. This mineral is relatively soft, with a Mohs hardness of 3.5. It is also quite brittle. ## Colors and Varieties Fluckite is typically colorless or has a delicate pink to violet tint. No distinct color varieties or commercial varieties are recognized. ## History and Name The mineral was discovered in the Gabe Gottes mine in Sainte-Marie-aux-Mines (Markirch) in the Vosges, France. It was described in 1980 by Halil Sarp, Pierre Perroud, and Jean Deferne. The name "fluckite" was given in honor of the French amateur mineralogist Pierre Fluck (born 1947), in recognition of his contribution to the study of Vosges mineralogy. ## Uses Fluckite has no industrial significance. It is solely an object of interest for collectors specializing in rare minerals or minerals from specific localities (so-called "systematists").

Properties

Mohs hardness: 3.5-4
Color: colorless, pale pink, pale rose red
Luster: Vitreous
Streak: White
Density: 0
Cleavage: {010| perfect, {100} good; {101} poor.
Fracture: Uneven
Transparency: Transparent,Translucent
Crystal system: Triclinic

Diagnostic features

## Identification Amateur identification of fluckite is practically impossible and requires advanced analytical methods such as X-ray diffraction (XRD) or chemical analysis (EDS/WDS). Preliminary identification is based on the analysis of the occurrence locality (Gabe Gottes or Daniel mine) and co-occurring minerals, such as pharmacolite, picropharmacolite, or native arsenic. The characteristic pink color and small, bladed crystals can be an indication, but are not a uniquely diagnostic feature. ## Distinguishing from Similar Minerals Fluckite is visually indistinguishable from many other rare arsenates, especially from pharmacolite, picropharmacolite, and sainfeldite, with which it often co-occurs. Pharmacolite is its calcium analog, and picropharmacolite is its calcium-magnesium analog. Differentiation of these minerals is possible only through chemical composition analysis. ## Crystal Forms Fluckite forms elongated, bladed or acicular crystals, flattened parallel to {010} and elongated along [001]. These crystals group into radial aggregates, rosettes, and also form disordered clusters and coatings.

Geological environment

## Genesis Fluckite is a secondary mineral, forming in the oxidation (weathering) zones of arsenical ores, mainly in hydrothermal veins containing arsenic, nickel, cobalt, and silver. It forms as a result of the reaction of arsenic-rich solutions with calcium- and manganese-bearing minerals. ## Mineral Associations This mineral most often occurs in association with other arsenates. At the type locality (Gabe Gottes), it was found with pharmacolite, picropharmacolite, sainfeldite, gypsum-pharmakolite, rauenthalite, irhtemite, as well as native arsenic, pharmacolite, and erythrite. In the Daniel mine, it co-occurs with native arsenic, löllingite, and tennantite. ## Localities Fluckite is an extremely rare mineral, known from only a few localities worldwide. The most important and confirmed occurrences are: - **France**: Gabe Gottes mine in Sainte-Marie-aux-Mines, Vosges (type locality). - **Germany**: Daniel mine in Wittichen, Black Forest.

Rarity

Very rare

For collectors

## Quality Criteria The quality of fluckite specimens is primarily assessed based on the richness and visibility of crystals on the rock matrix. Since the crystals are microscopic, specimens with dense, well-formed aggregates of intense, pink coloration are most highly valued. The aesthetics of the matrix and the presence of rare associated minerals, which increase the scientific and collector value of the specimen, are also important. ## Popular Localities Specimens from the type locality – the Gabe Gottes mine in France – are by far the most valued and sought after by collectors. Material from the Daniel mine in Germany is also valuable, but historically less accessible.

Care and storage

## Cleaning Fluckite specimens should be cleaned with the utmost care, using only compressed air to remove dust. Due to its brittleness and potential solubility in water, contact with liquids, including water and alcohol, should be avoided. Mechanical cleaning, even with a soft brush, is discouraged due to the risk of damaging the delicate crystals. ## What to Avoid Contact with water, acids, and other chemicals must be strictly avoided. The mineral is sensitive to changes in temperature and humidity. It should not be heated or exposed to direct sunlight, which can cause dehydration and destruction. ## Storage Fluckite requires storage under stable conditions. It is best kept in a closed, padded "micromount" box, which protects against dust, mechanical damage, and sudden changes in humidity. Display should be away from heat and light sources.