What is a natural, inorganic substance with characteristic chemical composition and usually structure?

• A. Mineral
• B. Rock
• C. Metal
• D. Crystal

Answer: (A)

A mineral is a natural, inorganic solid with a definite chemical composition and a crystalline internal structure. This combination is what sets minerals apart: they form through geological processes, have a specific chemical formula, and exhibit an orderly arrangement of atoms in a crystal lattice. Rocks, by contrast, are made up of multiple minerals and can include organic material, so they don’t have a single fixed composition. A crystal refers to the ordered arrangement of atoms, which minerals typically display, but crystals can be synthetic or organic as well, so the term alone isn’t the defining natural-inorganic substance. Metals describe elements or alloys and don’t capture the mineral’s fixed composition and crystal structure as a whole.