Paramelaconite

Chemical formula: Cu₁+₂Cu₂+₂O₃

A rare black copper oxide, forming characteristic, lustrous crystals with a square cross-section.

## Characteristics Paramelaconite is a rare copper oxide in which copper occurs in two oxidation states (Cu⁺ and Cu²⁺). It forms well-developed, lustrous crystals with a short- or long-prismatic habit, terminated by a bipyramid. The cross-section of the crystals is square, corresponding to its tetragonal internal structure. They are usually small, rarely exceeding a few millimeters in length. This mineral is completely opaque and ranges in color from pitch black to black. ## Physical Properties The hardness of paramelaconite on the Mohs scale is approximately 4.5, placing it in the group of minerals with medium hardness. It is characterized by a very high density, ranging from 6.04 to 6.11 g/cm³, which is a result of its high copper content. The luster is described as submetallic, meaning it is similar to metallic but slightly weaker. It is a brittle mineral. ## Colors and Varieties Paramelaconite occurs exclusively in black or brownish-black. No colored or commercial varieties are known. ## History and Name The name of the mineral refers to its chemical and physical similarity to melaconite (a historical name for tenorite, CuO) and the Greek word *para* meaning "near" or "beside". It was first described by George A. Koenig in 1891 based on specimens from the Copper Queen Mine in Bisbee, Arizona, USA, which remains its type locality. ## Applications Due to its great rarity, paramelaconite has no industrial application. However, it is a highly valued and sought-after collector's mineral, especially specimens from the type locality.

Properties

Mohs hardness: 4.5
Luster: Sub-Metallic
Streak: Brownish black
Density: 6.04-6.11
Cleavage: Distinct on {101}, {011}
Fracture: Sub-Conchoidal to Uneven
Transparency: Opaque
Crystal system: Tetragonal

Diagnostic features

## Identification Key diagnostic features of paramelaconite include its black color, submetallic luster, high density, and characteristic form of tetragonal, prismatic crystals with a square cross-section. The brownish-black streak is also an important clue. Occurrence in association with other secondary copper minerals is typical. ## Distinguishing from similar minerals Paramelaconite is often confused with tenorite (melaconite), which has a very similar composition and appearance. However, tenorite crystallizes in the monoclinic system and rarely forms such well-developed crystals as paramelaconite, occurring more often as coatings or earthy aggregates. It is distinguished from cuprite by its black color (cuprite is red) and different crystallographic system. Goethite can form black, lustrous crystals, but its streak is characteristic, yellowish-brown. ## Crystal forms Crystals are most often prismatic, with a square cross-section, terminated by tetragonal bipyramid faces. They occur as single, overgrown crystals or in small groups. Pseudomorphs after cuprite crystals are also known.

Geological environment

## Genesis Paramelaconite is a secondary mineral, formed in the oxidation zones of copper ore deposits. It forms under dry and desert conditions as a result of the slow oxidation of primary copper sulfides and other copper minerals, such as cuprite. ## Mineral associations It most often co-occurs with other minerals from the oxidation zone. Typical associated minerals include cuprite, native copper, tenorite, malachite, goethite, as well as rarer copper oxides and sulfates. ## Localities The most important and historical locality for paramelaconite, from which the world's best specimens originate, is the Copper Queen Mine in Bisbee, Cochise County, Arizona, USA. Much less frequently and in the form of less perfect specimens, it has been found in several other places around the world, including mines in Cornwall (Great Britain) and the Algomah Mine in Michigan (USA).

Rarity

Very rare

For collectors

## Quality criteria The most highly prized paramelaconite specimens are those with sharp, well-formed, lustrous crystals of distinct tetragonal form. The size of the crystals is of great importance - specimens exceeding one centimeter are already exceptional. The value is also enhanced by the attractive placement of crystals on the rock matrix, especially in association with colorfully contrasting minerals, such as red cuprite or green malachite. ## Popular localities Almost all the best collector specimens come from one place - the Copper Queen Mine in Bisbee, Arizona. This locality is considered classic for this mineral, and specimens from there set the standard for quality. Finds from any other locality are extremely rare and generate great interest among specialized collectors.

Care and storage

## Cleaning Paramelaconite specimens should be cleaned very carefully, using a soft brush to remove dust. If necessary, distilled water can be used. Ultrasonic cleaners should be avoided, as they could damage the brittle crystals. ## What to avoid The mineral is sensitive to acids and strong chemicals. As a secondary mineral, it can be unstable and may transform into other copper minerals, so extreme fluctuations in temperature and humidity should be avoided. It should not be exposed to prolonged direct sunlight. ## Storage It is recommended to store specimens in closed, stable conditions, preferably in collector boxes or display cases, away from chemicals. This will protect them from mechanical damage and unfavorable environmental changes.