mixture of natural uranium oxides, representing the final oxidation and hydration stages of uraninite, that usually occurs as dense masses and crusts in many of the known uraninite localities. It varies widely in physical properties, appearance, and chemical composition; it usually contains oxides of lead and thorium and large amounts of water. Gummite, named in reference to the gumlike appearance of some varieties, is related to well-defined uranium oxides as limonite and wad are to iron and manganese oxides.