Cherty Redwall Limestone

Plomosa Mountains | La Paz County | Arizona
Cherty Redwall Limestone that is part of a Miocene slide block east of Plomosa Pass (now Quinn Pass), northern Plomosa Mountains. Chert is microcrystalline quartz - hard and chemically inert unlike the surrounding Redwall limestone which is soft and susceptible to dissolution by carbonic acid found in natural waters. (Photo by Jon Spencer)