Abstract: The clay mineralogy of a soil profile developed in a New England glacial till has been studied to a depth of 55 in. Degraded soil micas, probably produced by weathering, have been chloritized by both iron and aluminum hydroxide complexes. Aluminum and iron determinations and X-ray analyses indicate that iron chloritization has played the greater role. Citrate-extractable chlorite exists to a depth of 55 in. X-ray and heat stability data indicate that the chlorite is better developed or crystallized near the surface. X-ray and glycol retention data suggest that intense weathering at the surface has reduced the surface charge density of some of the degraded mica.