The abundance of iron in the earth's core means that the mineral can sometimes seep into the water in which you bathe and wash your hair. The Illinois Department of Public Health states that very small amounts of iron as low as 0.3 mg per liter of water can cause a discoloration of the water, which can translate to buildup and possibly staining of... Hair Buildup, Earth's Core, Remove Rust, Natural Hair Growth Tips, Into The Water, Curly Girl Method, How To Remove Rust, Hair Growth Tips, Natural Hair Growth