Paratacamite-(Mg)

Chemical formula: Cu<sup>2+</sup><sub>3</sub>(Mg,Cu<sup>2+</sup>)Cl<sub>2</sub>(OH)<sub>6</sub>

Paratacamite-(Mg) is a rare mineral from the halide group, a magnesium analogue of paratacamite, found in the oxidation zones of copper deposits.

## Characteristics Paratacamite-(Mg) is a rare secondary mineral belonging to the atacamite group. It forms very small, tabular or prismatic crystals, often aggregated into rosettes or spherulites, as well as crusts and coatings. Its crystals rarely exceed 1 mm in size. It is a magnesium analogue of paratacamite, meaning that magnesium substitutes for some of the copper in its crystal structure. ## Physical Properties This mineral is characterized by a vitreous luster. It is transparent to translucent. Due to the small size of its crystals, its physical properties, such as hardness or density, have not been precisely determined, but they are similar to paratacamite (hardness 3-3.5, density approx. 3.7 g/cm³). ## Colors and Varieties Paratacamite-(Mg) occurs in shades from light green to emerald green. No color or commercial varieties are distinguished. ## History and Name The mineral's name refers to its structural relationship with paratacamite and the dominance of magnesium (Mg) in a specific position within its chemical formula. It was approved as a new mineral by the International Mineralogical Association (IMA) in 2013 (IMA2013-014). It was described based on specimens from the Cu-Zn-Pb mine "Esperanza" in Lavrion, Greece, which is its type locality. ## Uses Paratacamite-(Mg) has no industrial application. It is of purely scientific and collector's interest as a rare member of the atacamite group.

Properties

Mohs hardness
3.5
Luster
Vitreous
Streak
Light green
Density
3.66
Cleavage
Perfect on {0001}
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Trigonal

Diagnostic features

## Identification Identification of paratacamite-(Mg) is very difficult and usually impossible without advanced analytical methods, such as Raman spectroscopy or chemical analysis (EDS/WDS). Preliminary identification is based on its green color, co-occurrence with other secondary copper minerals, and characteristic, fine, tabular crystals. It reacts with hydrochloric acid. ## Distinguishing from Similar Minerals It can be easily confused with other green, secondary copper minerals, such as paratacamite, atacamite, brochantite, or malachite. Differentiation from paratacamite requires confirmation of magnesium presence. Malachite reacts vigorously (effervesces) upon contact with hydrochloric acid, unlike paratacamite-(Mg). ## Crystal Forms It forms small, pseudohexagonal, tabular crystals, often grouped into rosettes, spherulitic aggregates, or forming druses and crusts.

Geological environment

## Genesis Paratacamite-(Mg) is a secondary mineral, forming in the oxidation zones (gossans) of copper, zinc, and lead ore deposits. It forms as a result of the action of saline waters (rich in chlorides) on primary copper minerals in a magnesium-rich environment. Its formation is often associated with the activity of seawater or saline groundwater. ## Mineral Associations It most often co-occurs with other minerals from the atacamite group (atacamite, paratacamite), as well as with anglesite, gypsum, chalcanthite, hemimorphite, and goethite. ## Localities The most important and well-documented occurrences of this rare mineral are: - "Esperanza" Mine, Lavrion District, Attica, Greece (type locality). - "Atenaisa" Mine, Lavrion District, Attica, Greece. - Several locations in the Antofagasta region of Chile, including Sierra Gorda.

Rarity

Very rare

For collectors

## Quality Criteria The collector's appeal of paratacamite-(Mg) specimens primarily depends on the richness and aesthetics of the crystal aggregates. Most valued are specimens with well-formed, distinct crystals forming rosettes or covering the rock matrix as a sparkling druse. The intensity and shade of the green color are also important. Contrast with associated minerals, such as white anglesite, enhances visual appeal. ## Popular Localities The most known and prized specimens, including the type material, come from the historic mining district of Lavrion in Greece. Specimens from this region are considered classic for this mineral.

Care and storage

## Cleaning Specimens should be cleaned only very carefully, using a soft brush to remove dust. Contact with water, especially acids, can damage or destroy the delicate crystals. The safest method is dry cleaning. ## What to Avoid All chemicals, including acids and detergents, should be avoided. The mineral is sensitive to moisture and can undergo alteration in an unstable environment. It should be protected from high temperatures and direct, prolonged exposure to sunlight. ## Storage It is recommended to store specimens in a dry place, in sealed containers or display cases, to protect them from dust, moisture, and mechanical damage. Due to the small size and fragility of the crystals, touching their surface should be avoided.

Sources

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