Which statement best distinguishes a mineral from a rock?

Which statement best distinguishes a mineral from a rock?

• A. A mineral is a pure, inorganic substance with a definite chemical formula and crystalline structure; a rock is made of one or more minerals.
• B. A mineral is always organic; a rock is inorganic.
• C. A mineral forms only in space; rocks form on Earth.
• D. A mineral is always a single element; rocks are compounds.

Answer: (A)

Minerals are naturally occurring inorganic solids with a definite chemical composition and a crystalline structure. Rocks are mixtures or aggregates of one or more minerals, so they do not have a single fixed composition or crystal arrangement. That combination is why the statement about minerals being inorganic with a specific formula and crystalline order, while rocks are built from (one or more) minerals, is the best description. For example, quartz has a precise SiO2 composition and a crystal lattice, while a rock like granite contains several minerals in varying proportions. The other options misstate key facts—minerals aren’t necessarily organic, and they aren’t always a single element or a single compound, and rocks aren’t defined by forming only on Earth.

Minerals are naturally occurring inorganic solids with a definite chemical composition and a crystalline structure. Rocks are mixtures or aggregates of one or more minerals, so they do not have a single fixed composition or crystal arrangement. That combination is why the statement about minerals being inorganic with a specific formula and crystalline order, while rocks are built from (one or more) minerals, is the best description. For example, quartz has a precise SiO2 composition and a crystal lattice, while a rock like granite contains several minerals in varying proportions. The other options misstate key facts—minerals aren’t necessarily organic, and they aren’t always a single element or a single compound, and rocks aren’t defined by forming only on Earth.