Pyrite Ore | Feed The Beast Wiki | Fandom
Pyrite Ore is an addition from spawns in The Nether in veins approximately the same size as a vein of Coal Ore. Pyrite Ore was described by GregoriusT, the creator of GregTech, as having a "Gaussian distribution probability" meaning that some chunks will have Pyrite Ore everywhere whereas other chunks may have no Pyrite Ore whatsoever for a long distance.