What substances contain sulphur?

Sulfur is found in a variety of substances, including natural minerals like pyrite (iron sulfide) and galena (lead sulfide). It is also present in amino acids such as cysteine and methionine, which are essential for protein synthesis. Additionally, sulfur is a key component of sulfuric acid (H₂SO₄), a widely used industrial chemical, and can be found in certain fossil fuels like coal and oil. Biological systems, including plants and microorganisms, also contain sulfur in various organic compounds.