Rcdox-C ondilions and Prccipitaliun of Iron and Copper 193 



salts, in concentrations that were not at once precipitated 

 by H2S, killed most of the microbes living in the water and 

 changed the ecological conditions; but the biocenosis of the mud 

 remained unaltered. Within a month, the heavy metals were 

 transformed from carbonates or hydroxides to sulfides or directly 

 precipitated as sulfides, and the sulphureta were restored by the 

 microbial reservoir of the sediment. The experiments may be of 

 significance for the reproduction of geomicrobiological processes 

 which took place during the genesis of beds of sulfidic ores, e.g., 

 of the copper shales of the Zechstein formation in Germany. 



REFERENCE 



1. Baas Becking, L. M. G.: Studies on the sulfur bacteria. Ann. Botany, 

 39:613-650, 1925. 



