454 SECONDARY LIMESTONE. 



Flint and pyrites are the only minerals which 

 have been observed in the limestones of this 

 class, if we may except crystals of carbonat of 

 lime. The first of these abounds principally in 

 the chalks, but it also occurs, generally under 

 slight modifications of aspect, in the compact 

 limestones. Pyrites is found almost solely in 

 these latter. 



