MINERAL PAINTS. 63 



The Alabama barite is of white, grayish and bluish colors, 

 sometimes stained with iron on the surfaces. In the localities 

 mentioned the barite is very pure and white ; but it has not as 

 yet, so far as known, been put upon the market from Alabama. 



Tripoli or Polishing Powder. 



Tripoli proper, the infusorial or diatomaceous earth or "fossil 

 flour" of organic origin, occurs abundantly in many localities 

 in the lower part of the state, e. g., in the recent swamp depos- 

 its near Mobile ; in the Second Bottom .deposits of the Alabama 

 River at Montgomery ; in the Buhrstone and Clayton formations 

 of the Tertiary ; the first two being of fresh water origin, while 

 the Tertiary beds, containing marine diatoms and radiolaria, 

 are oi marine origin. In view of the fact that this material 

 finds extended use in the covering of steam pipes, etc., it would 

 be well worth while to investigate some of the occurrences more 

 closely. Many details are given in the Report on the Costal 

 Plain of Alabama. 



Polishing powder of very different origin occurs in many lo- 

 cHi'iVq in Northern Alabama. This is the result of the thor- 

 ough leaching of the cherty limestones and dolomites of the 

 Knox Dolomite of the Silurian, and of the Fort Payne division 

 of the Lower Carboniferous. It is known as "rotten stone/' 

 and is a porous rock of finely divided siliceous matter. To fit 

 it for use as a polishing powder it must be crushed, ground and 

 bolted. The largest deposits are in Talladega and Calhoun and 

 Lauderdale counties. 



Some shipments have been made from the first named. 



Copperas, Alum, and Epsom Salts. 



These mineral salts occur in protected or sheltered places 

 where the rocks contain iron pyrites, the weathering of which 

 furnishes the sulphuric acid, and the country rock the iron, 

 alumina, and magnesia. Such occurrences are most numerous 

 in connection with the strata of the Devonian and Carboniferous 

 formations, and are common in the open caves under oVerhang- 

 ing rock ledges, known as "rock houses." 



In the dark' colored sandy clays of the Claiborne and next 



