Origin of clays

Abstract

The origin of clay minerals at or near the earth’s surface is, in the majority of cases, a process instability in other silicate minerals. It is rare to find clays resulting from aqueous precipitation processes. Most clays are the result of an incongruent dissolution process where the clay is the least soluble portion of the mineral reaction. In processes involving clays at temperatures and pressures above those of the earth’s surface, clays are most often the result of recrystallization processes. These two major processes, which in fact divide geological origins into two general classes, will be treated separately. A third process is precipitation from solution, though this is very rare.