Nickel

Chemical formula: Ni

Native nickel is a rare mineral from the native elements group, occurring as metallic grains and flakes in ultramafic rocks and meteorites.

## Characteristics Native nickel is a naturally occurring, crystalline form of the element nickel. It is extremely rare, most often found as small, irregular grains, flakes, or scales embedded in other minerals. Due to its origin, specimens often contain iron impurities, forming natural alloys such as awaruite or kamacite. Pure native nickel is silvery-white with a slight golden tint, and surfaces exposed to air may develop a thin layer of patina. ## Physical Properties Nickel is a ductile and malleable metal. It exhibits a strong, metallic luster, which may be slightly dulled by weathering processes. It is relatively hard and dense. It possesses magnetic properties, which is an important diagnostic feature. ## Colors and Varieties The color of native nickel is silvery-white to grayish-white, often with a yellowish or golden tint. It does not form color varieties but occurs in natural alloys with iron, which are classified as distinct minerals: - **Awaruite** (Ni₃Fe) - a nickel-rich alloy with a silvery-white color. - **Kamacite** ((Fe,Ni) or α-(Fe,Ni)) - an alloy with 5-10% nickel content, characteristic of iron meteorites. - **Taenite** (γ-(Ni,Fe)) - an alloy with higher nickel content (20-65%), also a component of meteorites. ## History and Name The name nickel comes from the German word "Kupfernickel" (copper devil), used by medieval miners in Saxony. They referred to an ore (nickeline, NiAs) that looked like copper ore but from which they could not smelt the metal. The element nickel was isolated and described by the Swedish chemist Axel Fredrik Cronstedt in 1751. Native nickel as a mineral was first described much later. ## Applications Native nickel has no direct industrial application due to its extreme rarity. It is solely an object of interest for collectors and a subject of scientific research, particularly in the context of ultramafic rock petrology and meteoritics. The vast majority of global nickel production comes from its sulfide ores (e.g., pentlandite) and lateritic ores.

Properties

Mohs hardness: 3.5
Color: White, bright silver
Luster: Metallic
Streak: Gray, metallic
Density: 0
Cleavage: None
Fracture: Hackly
Transparency: Opaque
Crystal system: Isometric

Diagnostic features

## Identification The key diagnostic features of native nickel are its silvery-white color with a yellowish tint, metallic luster, and magnetic properties. It occurs as small, irregular grains or flakes. It is malleable, meaning it will flatten rather than shatter when struck. ## Distinguishing from Similar Minerals Native nickel can be confused with other metallic native minerals: - **Native iron:** Usually has a grayer color and rusts more quickly to brown or black. Nickel has a characteristic yellowish tint. - **Native platinum:** Is chemically inert, heavier (higher density), and non-magnetic. - **Native silver:** Is brighter, whiter, more malleable, and non-magnetic. It tarnishes black over time. - **Awaruite:** Is an alloy of nickel and iron, visually almost identical. Differentiation requires chemical analysis (EDS/SEM). ## Crystal Forms Native nickel crystallizes in the isometric system, but well-formed crystals are extremely rare. It typically forms granular, scaly, flaky aggregates or occurs as irregular nuggets and placers embedded in the host rock.

Geological environment

## Genesis Native nickel forms under specific, strongly reducing conditions. Its main environments of formation are: 1. **Ultramafic rocks:** Occurs as a product of peridotite serpentinization processes, where it is released from olivine. It forms at low temperatures in the presence of strongly reducing fluids. 2. **Meteorites:** It is an important component of iron meteorites (octahedrites, hexahedrites) and some chondrites, where it occurs as natural alloys with iron (kamacite and taenite). 3. **Hydrothermal deposits:** Very rarely found in hydrothermal veins associated with mafic and ultramafic intrusions. ## Mineral Associations In terrestrial rocks, native nickel most commonly co-occurs with serpentine group minerals (antigorite, chrysotile), magnetite, chromite, heazlewoodite, awaruite, and native copper. In meteorites, it is mainly accompanied by kamacite, taenite, troilite, and schreibersite. ## Localities Confirmed occurrences of native nickel are scarce. The most important include: - **New Caledonia:** In serpentinite massifs, from which some of the best-documented terrestrial occurrences originate. - **Josephine Creek and Bogota, Oregon, USA:** Classic localities for awaruite (a nickel-iron alloy), often referred to as "josephinite." - **Piedmont, Italy, and the Kraubath region, Austria:** Occurrences in Alpine ophiolite massifs. - **Siberia, Russia:** In nickel-copper deposits in the Norilsk region. - **Poland:** Found as very fine grains in serpentinites in Lower Silesia (e.g., in the Gogołów-Jordanów massif).

Rarity

Very rare

For collectors

## Quality Criteria The collector appeal of native nickel primarily depends on its origin and form. Most valued are specimens with clearly visible, distinct grains or flakes exhibiting a pronounced metallic luster, set in a contrasting rock matrix (e.g., in serpentinite). Specimens from classic, historical localities are also more highly regarded. Due to its rarity, any well-documented native nickel specimen, even microscopic, holds scientific and collector value. ## Popular Localities For collectors, specimens from New Caledonia and historical samples from Oregon, USA (as awaruite/josephinite) are most sought after. Specimens of meteoritic origin (kamacite/taenite) form a separate, specialized category of collections.

Care and storage

## Cleaning Specimens of native nickel, especially those embedded in a rock matrix, should be cleaned very carefully. The safest method is to use a soft brush to remove dust. For loose contaminants, compressed air can be used. Avoid washing in water, which can accelerate oxidation and dull the surface. ## What to Avoid Nickel is susceptible to oxidation, so it should be stored in a dry environment. Contact with acids and other aggressive chemicals, which can permanently damage its surface, should be strictly avoided. Prolonged exposure to humid air can lead to the formation of a dull patina. ## Storage It is recommended to store native nickel specimens in a dry place, preferably in closed, padded collector boxes or display cases. To limit contact with atmospheric moisture, desiccants (e.g., silica gel) can be used. Specimens in matrix are generally more stable.