just remembered a thought i had a while ago
so, minecraft diamonds, right. light blue, shiny rocks that are super tough, found at the deepest depths of the world.
back when minecraft was in alpha and beta, its creator (who i shall not name) said one of the design influences of the game was Dwarf Fortress.
In dwarf fortress, the toughest material you can get your hands on for tools, weapons and armor is Adamantine - a light blue, shiny metal found at the deepest depths of the world.
A significant amount of the design of dwarf fortress's world is based loosely on older fantasy works - one such influence being Lord of the Rings, with Adamantine being a deliberate parallel to its Mithril.
Minecraft diamonds are indirectly based on mithril.