CEMENT RESOURCES: BANGOR LIMESTONE. 45 



Table II Composition of Shales and Clays near Trenton Limestones. 



*Trace. 



2. Bangor Limestone. 



Areal Distribution. The Bangor limestone of the Lower 

 Carboniferous, is extensively developed in Northern Alabama, 

 being well exposed along most of the railroads radiating from 

 Birmingham. It is in fact so widely distributed that a detailed 

 geological map would be required to give any adequate idea of 

 the location of its various outcrops. 



Chemical Composition. In the vicinity of Birmingham ,at 

 Blount Springs, at Bangor, at and near Trussville, this lime- 

 stone has been extensively used as a flux in the furnaces. In 

 consequence, numerous analyses are available, and very close 

 estimates can be made both of its normal composition and of 

 probable deviations from the normal. These analyses show that 

 the Bangor limestone will usually carrv 92 to 98 per cent, lime 

 carbonate ; I to 5 per cent, of silica ; and I to 2 per cent, alumina 

 and iron. .Normally it does not contain over i l / 2 per cent, mag- 

 nesium carbonate, though one exceptional analysis shows a lit- 

 tle over 8 per cent, of that constituent. 



It may. therefore, be considered as a very pure limestone, and 

 available for use in Portland cement making; requiring the ad- 

 dition of one- fourth to one-third of its weight of clay or shale. 



