Nickeline Mineral Overview
- Mineral name: Nickeline (also called niccolite)
- Mineral class: Arsenide
- Chemical formula: NiAs (nickel arsenide)
- Crystal system: Hexagonal
- Mohs hardness: 5–5.5
- Color range: Copper-red, bronze-red, pale metallic red
- Luster: Metallic
- Streak: Brownish-black
- Cleavage: Poor
- Fracture: Uneven
- Specific gravity: Approximately 7.6–7.8 (very dense)
- Transparency: Opaque
- Common locations: Germany, Canada, Norway, Morocco
- Uses: Nickel ore, collector mineral
- Similar minerals: Chalcopyrite, pyrrhotite, rammelsbergite
Naming and Classification
Nickeline is a nickel arsenide mineral, historically known as niccolite.
Its name is derived from the German word Kupfernickel (“devil’s copper”), used by miners who mistook it for copper ore but couldn’t extract copper from it.
Nickeline is an important member of the arsenide mineral group, containing:
- Nickel (Ni)
- Arsenic (As)
Physical and Optical Characteristics
Nickeline typically occurs as:
- Massive or granular material
- Rare hexagonal crystals
- Disseminated grains in ore bodies
Its most distinctive feature is its copper-red metallic color, which may appear:
- Pale bronze
- Reddish metallic
- Tarnished to gray or black over time
The luster is metallic, often bright on fresh surfaces.
With a Mohs hardness of 5–5.5, it is moderately hard.
Tarnish Behavior (Key Feature)
Nickeline often:
- Tarnishes quickly when exposed to air
- Develops gray or black surface coatings
Freshly broken surfaces show the characteristic reddish metallic color, which is a key identification clue.
Chemical Composition and Structure
Nickeline is composed of:
- Nickel (Ni)
- Arsenic (As)
It has a relatively simple composition compared to many ore minerals, forming a hexagonal crystal structure.
Formation and Geological Occurrence
Nickeline forms in hydrothermal environments, particularly in:
Hydrothermal Veins
- Associated with nickel and cobalt deposits
Magmatic and Metamorphic Settings
- Found in ultramafic rocks
- Occurs in contact metamorphic zones
Typical formation conditions include:
- Moderate to high temperatures
- Arsenic-rich fluids
It is commonly associated with:
- Cobaltite
- Rammelsbergite
- Skutterudite
- Quartz and calcite
Common Locations
Nickeline is found in several important mining regions:
- Germany: Historic deposits (type locality)
- Canada: Sudbury Basin (major nickel region)
- Norway: Classic European occurrences
- Morocco: Notable modern specimens
These areas are known for nickel and cobalt mineralization.
Uses and Practical Significance
Nickeline is important for:
Nickel Ore
- Source of nickel, used in:
- Stainless steel
- Batteries
- Alloys
Collector Mineral
- Valued for its unusual reddish metallic color
It is less commonly used as an ore compared to pentlandite but still contributes to nickel production.
Safety Considerations
Nickeline contains arsenic, so:
- Avoid inhaling dust
- Handle with care
- Wash hands after handling
Similar and Related Minerals
Nickeline can resemble:
- Chalcopyrite: More yellow and brassy
- Pyrrhotite: More bronze and magnetic
- Rammelsbergite: Silvery rather than reddish
The reddish metallic color is the most important distinguishing feature.
Identification Notes for Collectors
- Look for copper-red metallic mineral
- Check for tarnish (darkening over time)
- Note high density (feels heavy)
- Observe moderate hardness (5–5.5)
- Consider association with nickel and cobalt ores
Nickeline is a nickel arsenide mineral, recognized for its distinctive reddish metallic color and role as a nickel ore, making it both economically important and visually unique among metallic minerals.