Which gemstone is composed of just one element?

• A. Quartz
• B. Ruby
• C. Diamond
• D. Emerald

Answer: (C)

Diamonds stand out because they are made entirely of carbon atoms arranged in a crystal lattice. An element is a substance that contains only one type of atom, and carbon in this solid form makes diamond a pure element as a gemstone. The other options are minerals that form compounds: quartz is silicon dioxide (two elements, silicon and oxygen); ruby is aluminum oxide with trace chromium for color; emerald is a beryl (beryllium aluminum silicate) with various trace elements. Those materials are composed of multiple elements, not just one. So diamond is the gemstone composed of a single element.