Friedrichite

Chemical formula: Cu¹⁺₅Pb²⁺₅Bi³⁺₇S²⁻₁₈

Friedrichite is a rare sulfosalt of copper, lead, and bismuth, forming acicular crystals with a metallic luster.

## Characteristics Friedrichite is a rare mineral from the sulfosalt group, composed of copper, lead, bismuth, and sulfur. It occurs as acicular or prismatic crystals, which can reach up to 2 cm in length. These crystals often form tangled or radial aggregates. Visually, it is an opaque mineral, with a silvery-gray color and a metallic luster. ## Physical Properties This mineral is characterized by a hardness ranging from 3.5-4 on the Mohs scale. Its density is quite high, approximately 6.98 g/cm³. The luster is distinctly metallic. Due to its opacity, it does not transmit light. ## Colors and Varieties Friedrichite occurs in a uniform, silvery-gray color. No colored varieties or trade names are known. ## History and Name The mineral's name honors Professor Günther Friedrich (1929–1992), a German mineralogist from the University of Aachen, who made significant contributions to ore deposit research. Friedrichite was officially recognized as a new mineral species in 1977, following its discovery at a historic locality. ## Uses Due to its extreme rarity, friedrichite has no industrial applications. It is solely an object of interest for collectors specializing in rare minerals and for scientific institutions.

Properties

Mohs hardness
3.5-4
Luster
Metallic
Density
6.98
Transparency
Opaque
Crystal system
Orthorhombic

Diagnostic features

## Identification Friedrichite is identified by its characteristic appearance – silvery-gray, metallic needles or prisms. Its high density is also a helpful feature. However, final identification requires advanced analytical methods, such as X-ray diffraction (XRD) or chemical analysis (EDS/WDS), due to its similarity to other sulfosalts. ## Distinguishing from Similar Minerals This mineral can easily be confused with other acicular lead and bismuth sulfosalts, such as aikinite, bismuthinite, gladite, or hammarite, with which it often co-occurs. Visual differentiation of these minerals is practically impossible without specialized laboratory analyses. ## Crystal Forms Friedrichite crystals have the form of elongated needles or prisms, often with visible longitudinal striations. They usually form aggregates of tangled masses or chaotically arranged needles within the host rock, which is quartz.

Geological environment

## Genesis Friedrichite is a hydrothermal mineral. It forms in quartz veins cutting gneisses and amphibolite schists. Its crystallization occurs under moderate temperature conditions in association with other sulfides and sulfosalts. ## Mineral Associations This mineral often occurs in association with other sulfosalts from the aikinite-bismuthinite series, such as aikinite, gladite, and hammarite. It also co-occurs with quartz, chalcopyrite, galenobismutite, and native bismuth. ## Localities The type locality and the only confirmed occurrence of friedrichite in the world is the historic Sedl mine, located on the slope of Mount Nasenkopf, in the Hollersbachtal valley, near Bramberg am Wildkogel in the state of Salzburg, Austria.

Rarity

Extremely rare

For collectors

## Quality Criteria The most valuable friedrichite specimens are those that contain well-formed, undamaged, and clearly visible acicular crystals, contrasting with the light quartz matrix. The size of the crystals and the richness of the aggregation on the specimen significantly increase its collector's value. Given that it is typically a microscopic mineral, specimens with crystals visible to the naked eye are particularly prized. ## Popular Localities The only source of friedrichite specimens is its type locality – the historic workings on Mount Nasenkopf in Austria. Material from this location is extremely rare and sought after by specialized collectors of systematic minerals and rare sulfosalts.

Care and storage

## Cleaning Friedrichite specimens should be cleaned very carefully, preferably using compressed air to remove dust. Avoid contact with water and any chemical agents. If it is necessary to remove dirt, a soft, dry brush can be used. ## What to Avoid Avoid contact with water, acids, detergents, and other chemicals that can cause oxidation and damage to delicate crystals. The mineral is relatively soft, so it must be protected from scratches and impacts. It should not be heated or exposed to sudden temperature changes. ## Storage It is recommended to store specimens in a dry place, in closed collector's boxes (so-called "micromount boxes"), to protect them from dust, moisture, and mechanical damage. Display should be in sealed display cases away from direct sunlight.

External references

Sources

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