Difference Between Pyrite and Chalcopyrite

Main Difference – Pyrite vs Chalcopyrite

A mineral is a naturally occurring solid, inorganic substance. Minerals are formed via geological processes. They have a definite chemical composition. Therefore, we can distinguish different types of minerals according to their chemical composition. Pyrite and chalcopyrite are also inorganic solid substances and are naturally occurring minerals. The main difference between pyrite and chalcopyrite is that the chemical composition of pyrite is FeS₂ whereas the chemical composition of chalcopyrite is CuFeS₂.

Key Areas Covered

1. What is Pyrite
      – Definition, Chemical Composition, Properties
2. What is Chalcopyrite
      – Definition, Chemical Composition, Properties
3. What is the Difference Between Pyrite and Chalcopyrite
      – Comparison of Key Differences

Key Terms: Chalcopyrite, Copper, Exothermic Reaction, Gold, Iron, Luster, Minerals, Pyrite, Sulfur

What is Pyrite

Pyrite is a yellow color mineral with a bright metallic luster. It is also known as fool’s gold because it bears a resemblance to gold. The chemical composition of this mineral is FeS₂ or iron disulfide. It is considered as the most common sulfide mineral.

Figure 1: A Pyrite Bar

Its color is described as brass-yellow. This mineral has an isometric crystal system. The molar mass of one formula of FeS₂ is about 119.98 g/mol. Pyrite is an opaque mineral and has a metallic luster. This mineral can be formed in any type of environment, at high temperatures or low temperatures. But it is unstable in the environment. Pyrite always exists under formation or destruction. When exposed to air and water, pyrite is decomposed into iron oxide and sulfates.

Sulfates formed while decomposition of pyrites can cause acid drainages when combined with water. This forms sulfuric acid and causes acid drainage. Pyrite decomposition is an exothermic reaction. It can cause dust explosions in coal mines.

Even though pyrite is composed of iron and sulfur as elements, it is not used as a source for the production of either of the elements. Iron can be easily obtained from ores where no sulfur contamination is present. The most important use of pyrite is as a gold ore since pyrite and gold both are formed under similar conditions. However, the amount of gold present in these ores are very less, about 0.25%. Sometimes, pyrite is used as a gemstone. It can be cut and carved into desired shapes. These stones are used to make jewelry.    

What is Chalcopyrite

Chalcopyrite is a mineral having the chemical composition of CuFeS₂. It is a brass-yellow color mineral. It is the most important source for the production of commercially important copper. This mineral naturally occurs in sulfide deposits. It looks very similar to pyrite.

Figure 2: Chalcopyrite

Chalcopyrite can be distinguished from pyrite due to its iridescent tarnish appearance. This mineral is often mistaken for gold due to the brass-yellow color. Chalcopyrite is less hard; it is brittle and will shatter if struck. It can be easily scratched with a nail. It has a high specific gravity; 4.1-4.3.

Chalcopyrite is an opaque substance. The crystal system of this mineral is tetragonal. It has a greenish black streak. A streak of a mineral is the color it displays when it is finely powdered. When exposed to the atmosphere, chalcopyrite can form several different oxides, hydroxides, and sulfates. Some chalcopyrite ores contain zinc, silver or gold as associated elements.

Copper can be obtained by roasting chalcopyrite. Complete roasting causes the formation of Cu metal where the partial roasting causes the formation of Cu₂S.

Difference Between Pyrite and Chalcopyrite

Definition

Pyrite: Pyrite is a yellow color mineral with a bright metallic luster.

Chalcopyrite: Chalcopyrite is a mineral having the chemical composition of CuFeS₂.

Chemical Composition

Pyrite: The chemical composition of pyrite is FeS₂.

Chalcopyrite: The chemical composition of chalcopyrite is CuFeS₂.

Presence of Copper

Pyrite: Pyrite doesn’t contain copper.

Chalcopyrite: Chalcopyrite contains copper.

Hardness

Pyrite: Pyrite is relatively hard.

Chalcopyrite: Chalcopyrite is brittle and can be easily scratched with a nail.

Specific Gravity

Pyrite: The specific gravity of pyrite is about 4.9-5.2.

Chalcopyrite: The specific gravity of chalcopyrite is around 4.1-4.3.

Crystal System

Pyrite: The crystal system of pyrite is isometric.

Chalcopyrite: The crystal system of chalcopyrite is tetragonal.

Conclusion

Minerals are naturally occurring inorganic substances that have a definite chemical composition. Each and every type of mineral is different from each other depending on the chemical composition. The main difference between pyrite and chalcopyrite is that the chemical composition of pyrite is FeS₂ whereas the chemical composition of chalcopyrite is CuFeS₂.

References:

1. “Pyrite.” Geology, Available here.
2. “Chalcopyrite.” Geology, Available here.
3. “Chalcopyrite.” University of Minnesota’s Mineral Pages: Chalcopyrite, Available here.

Image Courtesy:

1. “Pyrite bar (Missouri, USA – probably from the Buick Mine in Iron County, Missouri)” by James St. John (CC BY 2.0) via Flickr
2. “Chalcopyrite 1” By Lloyd.james0615 – Own work (CC BY-SA 3.0) via Commons Wikimedia