70 MINERAL RESOURCES OF ALABAMA. 



The rounded, waterworn quarts pebbles are abundant in the 

 Lafayette formation, which is a mantle of sands and pebble cov- 

 ering more or less completely all the central and lower parts of 

 the state. Usually the pebbles are imbedded in a red sandy clay 

 which acts as a cement holding them in place and forming a 

 road surface, scarcely if at all inferior to that made by the chert. 

 In nearly every county of the state from Tuscaloosa to the Gulf, 

 these clay pebble beds of suitable character occur, and there is 

 no reason why any of these counties should lack good roads. 



Broken limestone and dolomite, are the most common mate- 

 rial in some of the counties of the Tennessee valley, and in parts 

 of the Coosa valley, and the widely distributed limestones of 

 the Lower Carboniferous and Silurian formations of the north- 

 ern part of the state furnish an inexhaustible supply. 



For ballast, all the above mentioned road materials have been 

 utilized, and in addition to these broken up sandstones and fur- 

 nace slags. 



Millstones, Grindstones and Whetstnoes. 



The conglomerates of several formations of the state, espe- 

 cially of the Weisner Quartzite, the Coal Measures and the 

 Lafayette are capable of yielding good millstones, and locally 

 they have been so used, and in the early days some of them 

 had well established reputations. 



For grindstones the sandstones of the Cambrian and of the 

 Red Mountain and Coal Measures formations, have been 

 found suitable, and certain thin laminated sandy shales of the 

 Coal Measuers have served for whetstones of very good quality. 



Asphaltum, Maltha, Petroleum, and Natural Gas. 



The asphaltum and maltha here referred to are the solid 

 and semi-solid products resulting from the desiccation of the 

 fluid petroleums. 



These and petroleum are most common in the Lower Car- 

 boniferous rocks of Russellville and Moulton valleys and of 

 the southern slopes of the Little Mountain of the Tennessee 

 valley region. They occur in the highly fossiliferous crinoidal 

 limestones and the course-grained sandstones of the formation, 



