Natural generation [edit | edit source]. Iron occurs only around from bedrock to slightly above sea level (layers 1-63). However, almost all of the iron ore will be at the lower levels. On average, there are about 77 iron ores per chunk.Veins can vary in size, but the most common is 2×2×2.ron occurs only around from bedrock to slightly above sea level (layers 1-63). However, almost all of the iron ore will be at the lower levels.