Paxite

Chemical formula: CuAs<sub>₂</sub>

Paxite is a rare copper arsenide, forming metallic, tabular crystals and granular aggregates, found in hydrothermal veins.

## Characteristics Paxite is a rare mineral from the arsenide group, chemically a copper arsenide. It occurs as small, tabular or bladed crystals, often forming radial or granular aggregates. Its surface has a characteristic metallic luster. It is an opaque mineral, with a tin-white color that quickly tarnishes and darkens to brown or black in air. ## Physical Properties This mineral is characterized by a Mohs hardness of 2, making it very soft. It has a relatively high density, ranging from 8.02 to 8.11 g/cm³. It possesses perfect cleavage in one direction. ## Colors and Varieties Fresh paxite has a tin-white color with a metallic luster. When exposed to air, its surface quickly oxidizes, first taking on a brown hue, and eventually a dull black. No varieties are distinguished. ## History and Name The mineral's name comes from the Latin word "pax" meaning "peace," which refers to its discovery in the Svornost mine (Czech for "concord," "unity") in Jáchymov, Czech Republic. It was first described in 1940 by Czech mineralogists Johan and Hak, although its status as a distinct mineral species was questioned for some time and finally confirmed in 1961. ## Uses Paxite has no industrial significance. It is solely an object of interest for collectors specializing in rare minerals and a subject of scientific research.

Properties

Mohs hardness: 2
Luster: Metallic
Streak: Black
Density: 8.02 - 8.11
Cleavage: Perfect on {001}
Fracture: Uneven
Transparency: Opaque
Crystal system: Orthorhombic

Diagnostic features

## Identification Paxite can be identified by its tin-white color on a fresh fracture, which quickly darkens, its metallic luster, high density, and very low hardness. Its perfect cleavage in one direction is also characteristic. ## Distinguishing from Similar Minerals It can be confused with other arsenides such as löllingite, safflorite, or skutterudite, which are, however, much harder. It differs from domeykite (Cu₃As) by its crystal habit and perfect cleavage. Final differentiation requires advanced analytical methods, such as X-ray diffraction (XRD) or chemical analysis. ## Crystal Forms It forms thin, tabular or bladed crystals with a rhombic cross-section, often grouped into radial aggregates. It also occurs as granular aggregates and masses filling small fractures in the rock.

Geological environment

## Genesis Paxite is a hydrothermal mineral. It forms in low-temperature ore veins, most often in association with other arsenides and sulfides. ## Mineral Associations It co-occurs with minerals such as native arsenic, safflorite, löllingite, skutterudite, nickeline, rammelsbergite, native bismuth, native silver, uraninite, quartz, and calcite. ## Localities The most important and classic locality for paxite is the Svornost mine in Jáchymov (Czech Republic). It has also been found in mines in the Ore Mountains in Saxony (Germany), in the Cobalt-Gowganda area in Ontario (Canada), and in the Talmessi mine in Iran.

Rarity

Very rare

For collectors

## Quality Criteria For collectors, the most valuable specimens are those with well-formed, sharp crystals that retain their metallic luster. Rich crystalline aggregates on a rock matrix and rare associations with other minerals are also highly prized. Due to rapid oxidation, specimens that have preserved their original, tin-white color are particularly sought after. ## Popular Localities The most classic and valued paxite specimens come from its type locality – the Svornost mine in Jáchymov, Czech Republic. Material from this location is historically the most important and serves as a reference point for collectors.

Care and storage

## Cleaning Avoid cleaning with water and chemicals. The safest method is to use a soft brush or compressed air to remove dust. Any contact with moisture will accelerate the oxidation process. ## What to Avoid The mineral is very sensitive to moisture and oxygen from the air, which causes it to darken quickly. Avoid contact with water, acids, bases, and other chemicals. It should not be heated or exposed to prolonged sunlight. ## Storage Paxite specimens should be stored in a dry, airtight environment, preferably in sealed "perky boxes" with a desiccant. To slow down the oxidation process and preserve its metallic luster, some collectors store it in an inert gas atmosphere (e.g., argon).

Sources

IMA Mineral List (CNMNC)