Why do gems vary in color?

Gems vary in color due to factors such as their chemical composition, the presence of trace elements, and the way they interact with light. For instance, the presence of different metallic ions can impart distinct colors; for example, chromium gives emeralds their green hue, while iron may create blue in sapphires. Additionally, the gem's crystal structure can influence light absorption and reflection, further altering its perceived color. Environmental conditions during formation also play a role, leading to a wide spectrum of colors within the same type of gem.