Zircon

Zircon is the oldest known mineral on earth existing for an estimated 4.4 billion years old and unlocks a lot of key information to scientists about the early formations of earth. Zircon comes in a bunch of colors but most notably deep electric blue which unlike most gems is not caused by a mineral impurity or its chemical structure, its actually naturally existing radiation from uranium and thorium which alters the chemical molecular structure which reflects back blue light. That’s insane, super underrated gem

Hardness: 7.5
Composition: ZrSiO₄