What term is used for a solid, naturally occurring substance with a definite chemical composition and crystal structure?

• A. Mineral
• B. Rock
• C. Element
• D. Compound

Answer: (A)

A mineral is a solid, naturally occurring substance with a definite chemical composition and crystal structure. This means it forms through geological processes, has a fixed recipe of atoms, and those atoms are arranged in a repeating, orderly pattern. A rock, by contrast, is a mixture or aggregate of minerals, not a single substance with its own fixed composition and crystal order. An element is a pure substance consisting of one type of atom, which isn’t defined by a crystal structure in the context of minerals. A compound is a chemical combination of elements, which may or may not occur as a crystalline, naturally formed substance. The combination of natural occurrence, definite composition, and crystal structure uniquely describes a mineral.