Cu5FeS4, also known as chalcopyrite, is a mineral composed of copper, iron, and sulfur. It has a tetragonal crystal structure and is often found in hydrothermal veins and sedimentary deposits. Chalcopyrite is an important ore of copper, making it significant in mining and metallurgy. This mineral typically exhibits a brassy yellow color and can be confused with pyrite, or "fool's gold." Chalcopyrite is also used in the production of copper and sulfuric acid, contributing to various industrial applications. Its properties make it a valuable resource in the field of geology and mineralogy.