Paratacamite-(Ni)

Chemical formula: Cu²⁺₃(Ni²⁺,Cu²⁺)Cl₂(OH)₆

Paratacamite-(Ni) is a rare copper-nickel hydroxychloride, distinguished by its dark green color and trigonal crystals.

## Characteristics Paratacamite-(Ni) is a mineral from the atacamite group, being a hydrated copper-nickel chloride. It occurs as small, well-formed, trigonal crystals, often forming aggregates and crusts. Its most characteristic feature is an intense, dark green color. It is a secondary mineral, forming in the oxidation zones of nickel and copper ore deposits. ## Physical Properties This mineral is characterized by a hardness of 3 on the Mohs scale, making it relatively soft. Its density is determined to be 3.70 g/cm³. The crystals are transparent and exhibit a vitreous luster. The streak left on a plate is light, greenish. ## Colors and Varieties Paratacamite-(Ni) occurs in a uniform, dark green color. As a mineral defined by the dominance of nickel in a specific structural position, it does not form color varieties or commercial variants. Its name indicates its chemical composition, where "(Ni)" signifies that nickel is the dominant element in a given site within the crystal structure. ## History and Name The mineral's name refers to its relationship with common paratacamite and to the dominant nickel (symbol Ni) in its composition. It was approved as a new mineral species by the International Mineralogical Association (IMA) and first described based on specimens found in the Carr Boyd Rocks nickel mine in Western Australia. ## Applications Due to its extreme rarity, paratacamite-(Ni) has no industrial applications. It is solely an object of interest for collectors specializing in rare minerals and scientists studying the weathering processes of ore deposits.

Properties

Mohs hardness
3
Luster
Vitreous
Streak
Light green
Density
3.70
Cleavage
<mi>{10_11}</mi>
Fracture
Irregular/Uneven
Transparency
Transparent
Crystal system
Trigonal

Diagnostic features

## Identification Key diagnostic features include its dark green color, trigonal crystal habit, relatively low hardness (3 on the Mohs scale), and co-occurrence with other secondary copper and nickel minerals. A light green streak is also helpful in identification. However, definitive confirmation requires advanced chemical analysis (e.g., EDS) to confirm the presence of nickel as the dominant element. ## Distinguishing from Similar Minerals Paratacamite-(Ni) can be confused with other green, secondary copper minerals such as atacamite, paratacamite, brochantite, or malachite. It is distinguished from atacamite and paratacamite by the presence of nickel (analytically confirmed) and subtle differences in crystal habit (trigonal). It is distinguished from malachite by its lack of reaction with hydrochloric acid (malachite effervesces vigorously). Brochantite usually has a more acicular habit. ## Crystal Forms It forms small, tabular or rhombohedral crystals with a trigonal habit. They often occur as radial aggregates, rosettes, or as fine crusts on the host rock.

Geological environment

## Genesis Paratacamite-(Ni) is a secondary mineral that forms in the oxidation zones (gossans) of sulfide deposits rich in copper and nickel. Its formation is a result of the weathering of primary ore minerals in the presence of saline waters (source of chlorine). ## Mineral Associations This mineral co-occurs with other secondary copper and nickel minerals. In the type locality (Carr Boyd Rocks), it was found in association with gypsum, paratacamite, as well as rare nickel minerals such as gillardite and gaspeite. ## Localities The most important and type locality for paratacamite-(Ni) is the Carr Boyd Rocks nickel mine, located in the Menzies Shire region of Western Australia. This is the only confirmed and well-documented locality for this mineral worldwide.

Rarity

Very rare

For collectors

## Quality Criteria The most prized paratacamite-(Ni) specimens are those with well-formed, sharply terminated, and lustrous crystals of intense, dark green color. Contrast with the rock matrix and the presence of associated minerals are also important. Due to the small size of the crystals, specimens are primarily evaluated under a microscope, and their value increases with the size and perfection of individual crystals within an aggregate. ## Popular Localities The only source of collector specimens is the type locality - the Carr Boyd Rocks mine in Western Australia. Specimens from this location are highly sought after by collectors specializing in rare minerals and "micromount" specimens.

Care and storage

## Cleaning Specimens should be cleaned very carefully, using a soft brush to remove dust. Due to its softness, ultrasonic cleaners and hard brushes should be avoided. If liquid is necessary, distilled water is recommended, followed by immediate and thorough drying of the specimen. ## What to Avoid Contact with acids and other chemicals that may react with chlorides and hydroxides should be avoided. The mineral is susceptible to scratches due to its low hardness. It should not be heated or exposed to prolonged moisture. ## Storage Paratacamite-(Ni) specimens are best stored in separate, padded display boxes to prevent abrasion and mechanical damage. Protect from dust and moisture. Due to the small size of the crystals, they are often stored in "micromount" type boxes.

External references

Sources

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