Argonite

Argonite is a greenish-blue shining, ultra-durable metallic crystal. The Golden Horde mantains that it was first created by the gods, but later races were able to forge it with water, air, fire, earth, light, life, and void. In practice this meant a bucket of water (mixed in a ruby (hunted to extinction by triceratops herds) chalice with fish's breath (hard to come by even then)), a block of purified fire (too cold now thanks to entropy), bedrock (last succesfuly manipulated by the Crafters), solid light (the half-life of which resulted inthe last block decaying into a plume of lightstone 5 minutes ago), an Argonite acorn from the (long-vanished) Tree of Life, and solid void particle effects stuck together with Gorrilla Glue (the recipie was lost with the corruption of the Pigmen). It can be found as a crystal, a metal, or both.

Special properties
Argonite is hard enough to cut through bedrock.