Umangite

Chemical formula: Cu₃Se₂

Umangite is a rare copper selenide, characterized by a metallic luster and a distinctive reddish-purple color on a fresh surface.

## Characteristics Umangite is a rare mineral from the sulfide group, specifically a copper selenide. Its most characteristic feature is an intense, reddish-purple or bluish-purple color on fresh surfaces, which, however, quickly dulls and darkens upon exposure to air, becoming covered with a black tarnish. It most commonly occurs as fine-grained, massive aggregates embedded in the host rock. Well-formed crystals are extremely rare and appear as small, tabular or prismatic forms. ## Physical Properties This mineral is relatively soft, with a Mohs hardness of approximately 3. It is a brittle mineral with a high density, ranging from 5.62 to 6.49 g/cm³. It exhibits a strong, metallic luster on a fresh fracture, which, however, quickly fades. It is completely opaque. ## Colors and Varieties The dominant and virtually sole color of umangite is reddish-purple, often with a bluish tint. This color is a key diagnostic feature, although its instability should be noted. No named varieties of this mineral are distinguished. ## History and Name Umangite was first described in 1891 by Friedrich Klockmann. The mineral's name comes from its discovery locality – the Sierra de Umango mine in La Rioja province, Argentina. ## Uses Due to its rarity, umangite has no industrial applications. It is solely an object of interest for collectors of rare minerals and scientists.

Properties

Mohs hardness: 3
Color: Red, bluish red-black, iridescent violet-blue (tarnished)
Luster: Metallic
Streak: Black
Density: 6.44
Cleavage: poor, rectangular
Fracture: Irregular/Uneven,Sub-Conchoidal
Transparency: Opaque
Crystal system: Tetragonal

Diagnostic features

## Identification The most important diagnostic feature of umangite is its unique reddish-purple color on a fresh surface and a black, dull streak. This mineral is also relatively heavy. Its reaction to air – rapid dulling and blackening – is also very characteristic. ## Distinguishing from Similar Minerals Umangite is sometimes confused with bornite, which also exhibits colorful iridescence; however, bornite usually has more variegated, rainbow-like tarnishes, and its fresh surface is reddish-brown, not purple. Berzelianite (Cu₂Se) is silvery-white to gray. Digenite (Cu₉S₅) is blue to black. None of these minerals have such an intense purple color on a fresh fracture as umangite.

Geological environment

## Genesis Umangite is a hydrothermal mineral. It forms at low to medium temperatures in ore veins rich in selenium, cutting through sedimentary (sandstones, limestones) or volcanic rocks. It is one of the rarer copper selenides. ## Mineral Associations This mineral often co-occurs with other selenides, such as berzelianite, clausthalite, klockmannite, eucairite, and guanajuatite. It is also accompanied by other ore minerals like chalcopyrite, pyrite, and gangue minerals, mainly calcite and quartz. ## Localities The most important umangite localities worldwide include the historical type locality in Sierra de Umango, Argentina. Significant specimens also come from the Lehrbach and Zorge areas in the Harz Mountains, Germany. It also occurs in the Czech Republic (Bukovec, Předbořice), Sweden (Skrikerum), Bolivia, and the United States (Utah, Arizona).

Rarity

Rare

For collectors

## Quality Criteria The most highly valued umangite specimens are those that exhibit the largest possible surface area with an intense, fresh, reddish-purple color. Since this mineral rarely forms visible crystals, specimens with microcrystals visible under magnification are highly sought after. Rich association with other rare selenides also enhances attractiveness, especially if they create visible color contrasts. ## Popular Localities Classic and most prized specimens by collectors come from historical localities in the Harz Mountains in Germany and from the discovery site in Argentina. However, material from these localities is very difficult to acquire on the modern market.

Care and storage

## Cleaning Umangite specimens should only be cleaned mechanically, using a very soft brush to remove dust. All contact with water and chemical agents should be avoided, as they can accelerate the oxidation process and damage the mineral. ## What to Avoid The mineral is very sensitive to air and moisture, which cause it to quickly darken and decompose. Ultrasonic cleaners, acids, detergents, and any liquids should be strictly avoided. It should not be heated or exposed to prolonged light. ## Storage The best way to store umangite is to place it in a sealed, acid-free "perky box" or in a specialized container with a desiccant. Limiting air access is crucial for preserving the mineral's characteristic color.