I really hope they adapt the whole story at some point. From what I've heard we haven't even scratched the surface yet in season 1.

The characters in Land of the Lustrous are composed of living crystalline gemstones.

This is Phos, or more precisely, phosphophyllite. They are a hydrated form of zinc phosphate, and forms a greenish-blue transparent crystal.

The hair colors of the characters all correspond to the real-life crystal appearance of the corresponding gemstone. Dia (diamond) is white, Cinnabar (crystal mercury) is red, etc.