Crimtane Ore

Crimtane Ore is a rare pre-hardmode ore that was added in the 1.2 update. It has a luminescent blood red color and can be easily spotted underground due to its glowing effect. It can be found underground; more specifically, in the Crimson Biome's Chasms.

Crimtane is extremely rare to find, so it is not recommended that the player go mining for it. Summoning the Brain of Cthulhu and grinding it for the Crimtane Ore (and Tissue Samples) is much easier. The ore and tissue samples are used in the creation of Crimson Armor and its coinciding tool kit. The easiest way to summon the Brain Of Cthulhu is to craft the Bloody Spine from 15 Vertebrae (dropped by the Crimson Mobs).

It is also dropped by the Eye of Cthulhu (only in a world with the Crimson biomes instead of the Corruption biomes).