What is a mineral?

• A. A substance formed from living organisms.
• B. A natural, nonliving solid material with a definite chemical composition and crystal structure.
• C. A non-living solid without a definite chemical composition.
• D. A mixture of minerals that does not have a crystal structure.

Answer: (B)

A mineral is a natural, nonliving solid with a definite chemical composition and a crystal structure. That means its ingredients are a specific set of elements in fixed proportions, and the atoms are arranged in a repeating pattern that forms crystals. Minerals form through natural geological processes, and they are inorganic.

Think of quartz, which is made of silicon and oxygen in a specific arrangement, creating a crystalline lattice. That crystal arrangement is a hallmark of minerals.

This definition rules out living-organism substances, which are organic. It also rules out solids without a definite chemical makeup, and it rules out mixtures of minerals that don’t have a consistent crystal structure.