A diamond (from the ancient Greek αδάμας – adámas "unbreakable") is a re-arrangement of carbon atoms (those are called allotropes).
Diamonds have the highest hardness of any bulk (all one type) material. Because of this, many important industries use diamonds as tools for cutting and polishing things. Many of them are clear, but some of them have colors, like yellow, red, blue, green and pink. Diamonds of a different color are called "fancies".