RELATION OF CALCITE AND DOLOMITE 



447 



A few miles northeast of Sylacauga, where the field narrows and is 

 bordered on either side by parallel ridges, the following section (figure 

 13) is approximately correct: 



n. w. „ / s. E. 



So ° 



Figure 13. — Section through Marlle Valley at right Angles to the Strike 

 Phyllite similar to that on east side. i!. White marble, with opening of Alabama 



Marble Quarries Company here. 



Talladega phyllite 



RELATION OF CALCITE AND DOLOMITE 



111 many parts of the field the calcite marble is interbedded with dolo- 

 mite. The line between these two minerals is a very sharp one, as is 

 shown by the study of thin rock sections taken through the contact. Fre- 

 quently there is a thin film of iron ox id? separating the two minerals. 

 This interbedding of dolomite and calcite 

 has been observed in the Knox Dolomite 

 formation, which lies to the west of the 

 main marble belt for a considerable portion 

 of the field. Frequently these beds are very 

 thin. The following section (figure 14) is 

 taken from an outcrop in a sink about three 

 miles southwest of Gantts Quarry and illus- 

 trates on a small scale what takes place in 

 thicker beds elsewhere in the field. 



It is evident from the sharp line between 

 the calcite and the dolomite that there must 

 have been a difference in the character of 

 the originally deposited materials in these 

 beds. Whether this difference was physical 

 or chemical cannot be told from the present 

 investigation; but if there was not an original deposition of dolomite the 

 mineral originally occupying the place of the dolomite was exclusively 

 favored in the replacement process. 



CHARACTERISTICS OF THE MARBLE 



The Alabama marble is usually described as a fine-grained white mar- 

 ble. It exhibits more or less chloritic and talcose veining and clouding. 



DOLOM/T£ 



MARBLE 6 



OOLOM/r£ 

 MARBLE «? 



DOLOM/rE 



MAXBL£ 3' 



DOLO/1/TE 



Figure 14. — Section from the 

 Knox Dolomite Area jwst to the 

 west of the main Marble Belt. 



Showing the interbedded char- 

 acter of the sharply defined beds 

 of calcite marble and dolomite. 



