Although acquisition of mineral land except coal and iron land was prohibited, lands encompassed by railroad land grants sometimes were found later to contain minerals. When selling railroad grant lands, railroads frequently made a practice of reserving the minerals. Severance of mineral ownership from the surface estate by other landowners through reservation in deeds is common as well. Ambiguities concerning mineral reservations has been the source of much litigation. The mineral estate is sometimes then further divided by conveyance into undivided fractional interests.
Severed minerals are real property and usually are conveyed by mineral deed.