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Chalcopyrite is a copper iron sulfide mineral with the chemical formula CuFeS2. It is one of the most abundant sulfide minerals and the primary source of copper globally. Its distinctive brassy yellow color, often with iridescent tarnish, makes it recognizable. It is often found in association with other sulfide minerals like pyrite, sphalerite, and galena, and with gangue minerals such as quartz and calcite.
How to Identify
- Color
- Brassy yellow, often tarnishing to iridescent shades of blue, purple, red, and green. The fresh surface is distinctly brassy yellow.
- Luster
- Metallic.
- Texture
- Typically massive, granular, or disseminated. Crystals, when present, are usually small and tetrahedral or pseudotetrahedral.
- Crystal Form
- Tetragonal, often forming pseudotetrahedral crystals, but more commonly found as massive, disseminated grains or irregular aggregates. Striations are rare.
- Cleavage
- Poor to indistinct on {011} and {112}. It typically fractures rather than cleaves cleanly.
- Geological Environment
- Hydrothermal veins, porphyry copper deposits, skarns, volcanogenic massive sulfide (VMS) deposits, magmatic sulfide deposits, and sedimentary exhalative (SEDEX) deposits. It is a common accessory mineral in many igneous and metamorphic rocks.
Key Facts
- Hardness: 3.5-4 on the Mohs scale
- Specific Gravity: 4.1-4.3 g/cm³
- Crystal System: Tetragonal
- Color: Brassy yellow, often with iridescent tarnish
- Luster: Metallic
- Transparency: Opaque
- Fracture: Uneven to conchoidal
- Cleavage: Poor to indistinct
- Composition: Copper iron sulfide (CuFeS2)
Quick Check
- Color: Brassy yellow, often tarnished iridescent
- Luster: Metallic
- Streak: Greenish-black
Physical Characteristics
- Crystal Habit: Typically massive, disseminated, or granular. Crystals are rare, usually small pseudotetrahedra or sphenoids.
- Cleavage Type: Poor to indistinct on {011} and {112}. It tends to fracture rather than cleave.
- Fracture Type: Uneven to conchoidal.
- Tenacity: Brittle.
- Luster Type: Metallic.
Formation
Chalcopyrite forms in a wide range of geological environments. It is a primary mineral in many hydrothermal ore deposits, including porphyry copper deposits, skarn deposits, and volcanogenic massive sulfide (VMS) deposits. It also occurs in magmatic sulfide deposits associated with mafic and ultramafic intrusions, and in sedimentary exhalative (SEDEX) deposits. It can form at various temperatures and pressures, typically from moderate to high temperatures (200-600 °C) in hydrothermal systems.
Usage
Chalcopyrite is the most important ore mineral of copper, accounting for the vast majority of the world's copper production. Copper is essential for electrical wiring, plumbing, construction, electronics, and various industrial applications. It is also used in alloys like brass and bronze.
Age Distribution
Found in geological formations of all ages, from Precambrian to Cenozoic, wherever suitable conditions for hydrothermal or magmatic mineralization exist.
Where to Find
Chuquicamata, Chile
One of the largest open-pit copper mines in the world, renowned for its massive chalcopyrite deposits within a porphyry copper system.
Bingham Canyon Mine, Utah, USA
Another massive porphyry copper deposit, a significant source of chalcopyrite.
Sudbury Basin, Ontario, Canada
Famous for its magmatic nickel-copper sulfide deposits, where chalcopyrite is a major ore mineral.
Kidd Creek Mine, Ontario, Canada
A world-class VMS deposit with significant chalcopyrite mineralization.
Mount Isa, Queensland, Australia
Known for its large lead-zinc-silver and copper deposits, including substantial chalcopyrite.
Finding Tips
Look for Brassy Yellow Color
Chalcopyrite's distinctive brassy yellow color is a primary identifier. Be aware of iridescent tarnish, which can make it appear more colorful.
Check the Streak
A greenish-black streak is a key diagnostic feature that distinguishes it from pyrite (black streak) and gold (yellow streak).
Test Hardness
With a Mohs hardness of 3.5-4, chalcopyrite is softer than pyrite (6-6.5) and can be scratched by a steel knife.
Observe Associated Minerals
Chalcopyrite often occurs with other sulfide minerals (pyrite, sphalerite, galena) and quartz, which can help in identification and indicate a mineralized zone.
Consider Geological Context
Understanding the geological environment (e.g., hydrothermal veins, porphyry deposits) can narrow down possibilities and increase the likelihood of finding chalcopyrite.
Similar Rocks
Pyrite
FeS2
Also known as: Fool's Gold
Gold
Au
Also known as: Native Gold
Marcasite
FeS2
Also known as: White Iron Pyrites
Scientific Classification
- Mineral Class
- Sulfides
- Group
- Chalcopyrite Group
- Crystal System
- Tetragonal
- Chemical Formula
- CuFeS2
- Composition
- Copper (34.6%), Iron (30.4%), Sulfur (35.0%) by weight. Minor substitutions of zinc, silver, and gold can occur.
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