Bluesteel is a material used to make various hats and weapons. The Bluesteel Claw, Bluesteel Bathelm, and Bluesteel Viking Helm of Infinite Pillage use this texture.
Currently, only eight bluesteel items are available to players. The eight that you can obtain are the Bluesteel Fedora, Bluesteel Bathelm, Bluesteel Egg of Genius, Captain Bluesteel, Bluesteel Crown, Bluesteel Viking Helm of Infinite Pillage, Bluesteel Bathyspere and Bluesteel Warhelm of Rekt.
Association with Viridium
Viridium is an alloy of Bluesteel. This means it is formed by Bluesteel being "crushed" into microscopic crystals. Then, these crystals clump together making Viridium. Although there may be another metal in Viridium, ROBLOX has not gone in-depth on this subject.