CLAY 



Clay is a ubiquitous mineral resource that is found in virtually all 

 geologic horizons in varying concentrations and qualities. Clay is found 

 either where it is formed, adjacent to the weathered parent material (where 

 it is termed "residual"), or where it has been deposited by water (where it 

 is termed "sedimentary"). Residual clays may occur either as a uniform 

 mantle overlying the parent rock, or may accumulate into veins or dikes 

 alongside the parent rock. 



"Clays occupying veins or dikes are usually kaolin, or a decomposition 

 product of granite or feldspar, and commonly show definite lines of 

 demarkation" (Jones 1926). 



When sedimentary clays are deposited by water, they may be interspersed 

 with any other type of sedimentary deposit, such as coal or limestone. Clays 

 deposited as sediments may extend uniformly over large areas or may be quite 

 small lenses. Sedimentary clay particles are generally finer than those in 

 residual clay. When subjected to great pressures, the clay particles may con- 

 solidate to form shales. If shales are ground finely, they regain the charac- 

 teristic plasticity of clays (Jones 1926). 



There are four types of clays mined in Alabama: bentonite, kaolin, fire 

 clay, and common clay. Bentonite is a decomposition product of volcanic ash. 

 Bentonite is used as a binder in foundry sand or as drilling mud, and is 

 mined primarily in Lowndes County (Smith and Gilbert 1975). 



Kaolin is used for the manufacture of refractory (heat-resistant) 

 products. It is mined in Henry, Marion, and Barbour Counties, where it is 

 usually found in association with bauxite (aluminum ore) (Smith and Gilbert 

 1975). 



Fire clay is also used for refractory purposes, in making heat-resistant 

 bricks and ceramics. Fire clay is primarily mined in Calhoun, Blount, and 

 Walker Counties, where it is often found underneath coal strata, and is 

 subsequently mined in conjunction with coal operations (Smith and Gilbert 

 1975). 



Common clay accounts for over 80 percent of the clay mined in Alabama and 

 is used for building brick and lightweight aggregate (Corey 1976). Clays 

 occurring within Mobile and Baldwin Counties are found in small lenses within 

 the Miocene and PI io-Pleistocene (Citronelle Formation) deposits. The only 

 large area of exposed clay and the only clay mining operation within the two 

 coastal counties occurs near Clay City (Pensacola quadrangle) in southern 

 Baldwin County. At this site, the Fish River has exposed the 

 Miocene/Pliocene/Pleistocene strata. This clay is mined in shallow open pits 

 and is used for brick, tile, and sewer pipe (Moser and Chermock 1978). 



The Citronelle Formation (mid-Pliocene to early Pleistocene) and the high 

 terrace deposits (Pleistocene) are difficult to differentiate as they are 

 both composed of sand, clay, and some gravel (Moser and Chermock 1978, 

 Isphording and Lamb 1971). Clay reserves in the Citronelle Formation are 



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