Mixed iron (lat. Ferrum mixtum) is a geological formation that is a mixture of various rocks, mainly of iron origin. It is found in many places on Earth, but is especially common in folded mountain systems such as the Appalachians, Rocky Mountains and others.
Mixed iron is represented by a variety of geological formations. One of the most common is the rock-forming low-sulfide (mainly quartz-feldspathic) ultramafic association Porphyry, diorite, and less commonly dolerite. Most of it is concentrated in the interstices between mafic intrusions of basic composition. In some areas, iron mixed breeds even dominate the