Diamond

The stone everyone knows and loves
Diamonds are hardest material on earth but also very simple as they are just a single mineral of carbon, where as many gems are mineraloids meaning they contain multiple minerals

Diamonds come in more colors then people expect like blue, green, orange, purple, pink, black, gray, yellow and the rarest being red. Pink and red diamonds are some of the most unique gems because there isn’t actually anything in it causing a color like most gems, its an illusion! This illusion is called plastic deformation in which a deformity in the crystal structure reflects that light back at you, kind of like how you see rainbows through glass , except just one color!

Hardness: 10
Composition: C