Book 27, Question 76
What makes a mineral a gemstone?
A gemstone is a mineral, or sometimes another natural material, that is beautiful, tough enough to wear, and rare enough to be valued.
Diamonds, rubies, sapphires, and emeralds are well-known examples. Most gems start as rough stones that look dull until a gem cutter shapes and polishes them. A gem's color, clarity, and hardness all help decide how special it is.