Fuller’s earth. Also known as whitening clay, it gets its name from its utility in whitening sheep’s wool (work done by a “fuller”). It’s a natural clay rich in the minerals known as hydrous aluminum silicates, which give it its unique properties.
Saponin (Soapwort, Yucca, and others). Saponin is a compound found in several species of plants, especially those in the genus Saponaria. It is toxic to humans, but it has the ability to form a foam that binds to fats, much like a manufactured soap.
From the Crazy Useful Catalog:
Crazy Useful Things
A Dictionary of Natural Resources and Their Products