Which term refers to atoms in a gem that aren't part of its essential chemical composition?

• A. The main mineral components.
• B. Atoms in a gem that aren't part of its essential chemical composition.
• C. The isotopes of the mineral.
• D. The crystal faces.

Answer: (B)

The concept hinges on distinguishing atoms that are not part of the essential chemical formula of the gem. Atoms that are present in tiny amounts but aren’t part of the primary composition are impurities, also called trace elements. They sit in the crystal lattice and can noticeably affect properties like color, without changing the fundamental chemical formula of the mineral. The other ideas don’t fit because the main mineral components describe the essential composition, isotopes are variations of the same element’s atoms rather than extra atoms in the lattice, and crystal faces are just the exposed surfaces of the crystal.