Breithauptite

Chemical formula: NiSb

Breithauptite is a nickel antimonide, characterized by its distinctive copper-red color and metallic luster.

## Characteristics Breithauptite is a relatively rare mineral from the niccolite group, chemically classified as nickel antimonide. Its most recognizable feature is its unique, purplish, copper-red color, which is bright and intense on fresh fracture surfaces. Over time, it may become covered with a darker, sometimes iridescent tarnish. It typically occurs as granular aggregates, massive forms, or intergrown with other minerals. Less commonly, it forms small, hexagonal crystals with a tabular or prismatic habit. ## Physical Properties This mineral is opaque and exhibits a strong, metallic luster. Its Mohs hardness is 5.5, placing it in the same category as apatite. It is a brittle mineral with a density of approximately 7.6 g/cm³, which makes it noticeably heavy to the touch compared to most common minerals. ## Colors and Varieties The dominant and essentially only color of breithauptite is bright copper-red with a violet tint. No color or commercial varieties are distinguished. ## History and Name The mineral's name, given in 1840 by Julius Fröbel, honors August Breithaupt (1791-1873), a renowned German mineralogist and professor in Freiberg. Breithaupt was the first to describe this mineral in 1833 under the name "nickel antimonide" (Antimonnickel). ## Uses Due to its rarity and small accumulations, breithauptite has no significance as a source of nickel. However, it is a valued and sought-after collector's stone.

Properties

Mohs hardness
5.5
Color
Copper-red with a violet tint
Luster
Metallic
Streak
Reddish brown
Density
7.591
Cleavage
None
Fracture
Irregular/Uneven,Sub-Conchoidal
Transparency
Opaque
Crystal system
Hexagonal

Diagnostic features

## Identification The key diagnostic feature of breithauptite is its unique copper-red color with a violet tint, combined with a strong metallic luster and a reddish-brown streak. This combination is rare among other metallic minerals. Additionally, it is harder than most similarly appearing sulfides and arsenides. ## Distinguishing from Similar Minerals Breithauptite is sometimes confused with niccolite (NiAs), which, however, has a lighter, more reddish-pink color and a black streak. Native copper is more orange or reddish-brown, significantly softer (2.5-3 on the Mohs scale), and malleable. Bornite has a similar color but quickly develops a characteristic, purplish-blue, iridescent tarnish and is much softer (hardness 3). ## Crystal Forms Breithauptite crystals are rare. If they occur, they take the form of hexagonal, flattened tablets, short prisms, or pyramids. Most often, it is found as massive, granular, or disseminated aggregates within the host rock.

Geological environment

## Genesis Breithauptite is a hydrothermal mineral. It forms in ore veins rich in cobalt, nickel, and silver, which cut through carbonate rocks (limestone, dolomite). It forms under conditions of relatively high temperatures and low sulfur content. ## Mineral Associations It often co-occurs with other ore minerals such as niccolite, skutterudite, ullmannite, cobaltite, gersdorffite, maucherite, as well as native silver, native bismuth, calcite, dolomite, and barite. ## Localities Historically important and classic localities are in Germany (St. Andreasberg in the Harz Mountains; Schneeberg and Annaberg in Saxony). It is also known from the Cobalt-Gowganda region in Ontario (Canada), where it occurred in silver veins. Other reported localities include mines in the Czech Republic (Jáchymov) and the United States (Colorado).

Rarity

Rare

For collectors

## Quality Criteria The most prized specimens by collectors are those with well-formed, sharp crystals, which are very rare. Rich, massive aggregates with an intense, fresh color, contrasting with a light host rock (e.g., with white calcite), are also highly valued. Minimal tarnish and mechanical damage are important. ## Popular Localities The historical localities in Germany, especially in the St. Andreasberg region, are considered classic and yield the best specimens. Specimens from Cobalt, Canada, often in association with native silver, are also highly regarded in the collector's market.

Care and storage

## Cleaning Breithauptite specimens should only be dry-cleaned, using a soft brush to remove dust. Contact with water, and especially with acids, can lead to permanent damage and loss of luster. ## What to Avoid All chemicals, detergents, and ultrasonic cleaners should be strictly avoided. The mineral is sensitive to moisture and atmospheric agents, which can cause dulling and tarnish formation. It should not be heated or exposed to prolonged sunlight. ## Storage Breithauptite collections are best stored in dry, stable conditions, preferably in closed display boxes or cabinets away from sources of moisture. To prevent oxidation, desiccants can be used.

External references

Sources

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