Maucherite

Chemical formula: Ni<sub>₁₁</sub>As<sub>₈</sub>

Maucherite is a rare nickel arsenide, forming characteristic, tabular crystals with a metallic luster and a reddish hue.

## Characteristics Maucherite is a rare mineral from the arsenide group, consisting mainly of nickel and arsenic. It usually occurs in massive, granular aggregates, and well-formed crystals are rare. When they do appear, they take the form of thin, tabular or pyramidal crystals with a tetragonal outline. Fresh surfaces have a silvery-white color with a reddish or pinkish hue, which dulls over time and becomes covered with a darker, gray or greenish tarnish. ## Physical Properties This mineral is opaque and characterized by a distinct metallic luster. Its Mohs hardness is approximately 5, placing it in the same category as apatite. It is relatively dense, and its fracture is uneven. ## Colors and Varieties Maucherite is an idiochromatic mineral, meaning its color is a constant feature resulting from its chemical composition. The typical color is silvery-white with a distinct reddish or pinkish hue, often described as copper-red. On weathered surfaces, a green tarnish of secondary arsenic minerals, such as annabergite, may appear. ## History and Name The mineral was first described in 1913 by the German mineralogist Friedrich Grünling. The name "maucherite" was given in honor of Wilhelm Maucher (1879–1930), a German mineral collector and dealer from Munich, who provided the first samples for study. ## Uses Due to its rarity, maucherite has no industrial significance as a source of nickel. However, it is a prized collector's mineral, sought after for its unique chemical composition and associations with other rare nickel and cobalt minerals.

Properties

Mohs hardness: 5
Luster: Metallic
Streak: Grey-black
Density: 7.8-8.0
Cleavage: None
Fracture: Uneven
Transparency: Opaque
Crystal system: Tetragonal

Diagnostic features

## Identification Key diagnostic features of maucherite include its characteristic reddish-silvery color on a fresh fracture, metallic luster, and relatively high density. It often occurs in association with other nickel and cobalt arsenides. It reacts with nitric acid, coloring the solution green (from nickel). ## Distinguishing from Similar Minerals Maucherite is sometimes confused with nickeline, which also has a reddish hue. However, nickeline has a more intense, copper-red color and crystallizes in the hexagonal system. From other metallic minerals, such as bornite or pyrite, it is distinguished by its specific hue, hardness, and mineral associations. ## Crystal Forms Well-formed crystals are rare and usually small. They take the form of thin, square tablets or complex, pyramidal forms. Most often, it is found as radial aggregates, massive, granular clusters, or inclusions in other minerals.

Geological environment

## Genesis Maucherite is a hydrothermal mineral, forming in ore veins at relatively low to medium temperatures. It forms in environments rich in nickel and arsenic, and poor in sulfur. ## Mineral Associations It most commonly co-occurs with other nickel and cobalt arsenides, such as nickeline, rammelsbergite, skutterudite, safflorite, and löllingite. It is also often accompanied by native bismuth, native silver, calcite, dolomite, and barite. ## Localities Important historical and classic localities include: Eisleben and Mansfeld in Germany (type locality), Cobalt-Gowganda in Ontario (Canada), as well as some deposits in Saxony (Germany) and the Bou Azzer region (Morocco). It also occurs in Argentina, Australia, and the Czech Republic.

Rarity

Rare

For collectors

## Quality Criteria The most prized specimens by collectors are those with well-formed, sharp crystals, which are very rare. Rich aggregates with an intense, reddish-silvery color, contrasting with a light matrix rock (e.g., calcite or dolomite), are also highly valued. Association with other rare minerals, such as skutterudite or native silver, is also important. ## Popular Localities Specimens from classic European localities in Germany (Saxony, Hesse) are historically significant and sought after. However, currently some of the best specimens in the world, including those with well-formed crystals, come from the Cobalt region in Ontario, Canada.

Care and storage

## Cleaning Wet cleaning of maucherite is generally not recommended. Dust and loose dirt are best removed with a soft brush or compressed air. Contact with water can accelerate oxidation processes. ## What to Avoid Avoid contact with water, acids, and other chemicals that can react with arsenides and cause their decomposition. The mineral is sensitive to moisture, which leads to dulling and the formation of tarnishes. It should not be heated, as this can lead to the release of toxic arsenic fumes. ## Storage Maucherite specimens should be stored in a dry place, preferably in tightly sealed containers or display cases with controlled humidity. Using desiccants (e.g., silica gel) is good practice. Due to its arsenic content, hands should be washed after any contact with the mineral.

External references

https://en.wikipedia.org/wiki/https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FMaucherite