Nimite

Chemical formula: (Ni<sup>2+</sup>,Mg,Al)<sub>6</sub>(Si,Al)<sub>4</sub>O<sub>10</sub>(OH)<sub>8</sub>

Nimite is a rare, nickel-rich member of the chlorite group, forming microscopic, green crystals and aggregates.

## Characteristics Nimite is a mineral from the chlorite group, an hydrated nickel, magnesium, and aluminum silicate. It typically occurs as very fine, scaly crystals that form compact or earthy aggregates, as well as coatings and crusts. Due to the microscopic size of its crystals, its macroscopic features are difficult to observe; it most often appears as a green mass or coating on other rocks. ## Physical Properties Nimite crystals are very soft, with a Mohs hardness of approximately 3. This mineral has a vitreous luster, and in earthy aggregates, a dull or earthy luster. It is translucent to opaque. The density of nimite is approximately 3.1 g/cm³. ## Colors and Varieties Nimite ranges in color from yellowish-green to green, which is characteristic of nickel-bearing minerals. No named varieties are distinguished. ## History and Name The mineral's name comes from its discovery locality – The Bon Accord Nickel Mine in the Barberton Mountain Land, South Africa. It was approved as a new mineral by the International Mineralogical Association (IMA) in 1966. The name refers to the National Institute for Metallurgy of South Africa (NIM), in recognition of that institution's contribution to mineralogical research. ## Uses Nimite has no industrial application. It is of purely scientific and collector's interest, being a subject of interest for specialized collectors of rare minerals.

Properties

Mohs hardness
3
Luster
Vitreous, Dull, Earthy
Streak
Light green
Density
3.1
Cleavage
Perfect on {001}
Fracture
Uneven
Transparency
Translucent to opaque
Crystal system
Monoclinic

Diagnostic features

## Identification Identifying nimite with the naked eye is practically impossible and requires advanced analytical methods, such as X-ray diffraction (XRD) or chemical analysis (EDS/WDS). In the field, it can be suspected based on its characteristic green color, occurrence in association with other nickel minerals, and specific geological environment (altered ultramafic rocks). ## Distinguishing from Similar Minerals Nimite can be confused with other green secondary nickel minerals, such as nepouite, pimelite, or garnierite (a mixture of minerals). It is distinguished from other chlorites (e.g., clinochlore) by its high nickel content, which can only be determined by chemical analysis. ## Crystal Forms Nimite forms extremely fine, hexagonal or pseudohexagonal crystals with a platy or scaly habit. These crystals usually occur as rosette-like aggregates, compact masses, or earthy coatings.

Geological environment

## Genesis Nimite is a secondary mineral, forming in the weathering zones of nickel sulfide deposits. It forms as a result of hydrothermal alteration or weathering of nickel-rich ultramafic rocks (e.g., serpentinites). It can also crystallize in low-temperature veins cutting these rocks. ## Mineral Associations This mineral co-occurs with other nickel minerals and host rocks. Typical associated minerals include trevorite, violarite, millerite, nepouite, willemseite, as well as talc, magnesite, and quartz. ## Localities The most important and type locality for nimite is the Bon Accord mine in the Barberton district, South Africa. It is also known from several other localities worldwide, including Baldissero Canavese in Italy and nickel mines in the Ural region of Russia.

Rarity

Very rare

For collectors

## Quality Criteria As a rare and microscopically occurring mineral, nimite is not evaluated according to typical criteria such as crystal size or clarity. For collectors, specimens from the type locality (Bon Accord) are most valuable, where nimite forms distinct, rich aggregates of intense green color, contrasting with the host rock. Any specimen with analytically confirmed nimite presence is valuable from a scientific point of view. ## Popular Localities Specimens from the Bon Accord mine in South Africa, which is its type locality, are by far the most prized and sought after by collectors.

Care and storage

## Cleaning Nimite specimens are very delicate and usually occur as thin coatings or friable aggregates. Cleaning should be kept to an absolute minimum. If necessary, a very soft brush can be used to remove loose dust. Avoid water and any chemical agents. ## What to Avoid Contact with water, acids, and other chemicals that can damage or dissolve the mineral should be strictly avoided. As a very soft mineral, it is susceptible to scratches and mechanical damage. It should not be subjected to ultrasonic cleaning. ## Storage Nimite specimens should be stored in stable conditions, away from moisture and dust. It is best to keep them in closed collector's boxes to protect them from physical damage and contamination.

External references

Sources

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