36 MINERAL RESOURCES OF ALABAMA. 



Pire Clays. These are clays which do not fuse when sub- 

 jected to a high temperature, at least 2700 degrees Fahrenheit. 

 Semi-refractory clays which cannot withstand a temperature of 

 more than 2300 to 2400 degrees are sometimes called fire clays, 

 and are in fact used along with other more refractory clays in 

 the manufacture of certain classes of fire brick. The fire clays 

 of non-plastic character are known as flint clays, and have 

 nearly the composition of kaolinite. The only Alabama mater- 

 ial which might be classed as a flint clay occurs very abundantly 

 in the lower Claiborne or Buhrstone formation of the Tertiary. 

 It is, however, a highly siliceous material carrying as much as 

 85 per cent, of silica, and containing a great 1 number oi the sili- 

 ceous tests or shells of radiolaria. 



The plastic fire clays are rather widely distributed, occurring 

 in the Cambrian and Silurian formations, in the Lower Carbon- 

 iferous, and most probably in the Coal Measures, though none 

 has as yet been investigated from that horizon. The Lower 

 Cretaceous or Tuscaloosa formation, which stretches as a belt 

 around the southern and western edge of the older formations, 

 is perhaps the most important in respect of its clays of all sorts. 

 The following table will show the composition of refractory 

 clays from a number of localities, together with their melting 

 points. The bauxites of Cherokee county have been tested as 

 to their refractory qualities and from these tests it appears that 

 they may be advantageously used in connection with refractory 

 fire clays in the making of fire brick. Several analyses and fire 

 tests, of bauxites have been included in the table. 



Manufactories of fire brick are located at Bessemer, Ashby, 

 Brickyard, Fort Payne, etc. 



