Platinum Ore is the fourth tier of alternate ores, and considered one of the BEST ores in pre-harmode (the others being Hellstone, Demonite, and Crimtane). It is a material added in 1.2. It is used to craft various weapons, tools, and armor. It is less common than Tin, Lead, and Tungsten. When a new world is generated, there is a chance that it will generate instead of Gold Ore.
Platinum is one tier below Crimtane and one tier above Tungsten.