704 



W. N. Benson — Origin of Serpentine. 



twelve feet, but more usually only a few inches in thick- 

 ness, made up of limonite, with quartz, chalcedony and 

 carbonates of iron and magnesia, together with a little 

 chlorite or vermiculite, talc, and kaolin. Not infre- 

 quently the carbonates are entirely absent. This cover- 

 ing forms from either peridotite or serpentine, and in the 



Fig. 4. 



| v v v v v v v J Tilaites 



iuii2£S ne 



Fig. 4. The Dimite mass of Taguil surrounded by pyroxenite and 

 gabbro, showing the distribution of the serpentine. (After Wyssotsky, 

 simplified; Mem. Comm. Geol. Eussie, No. 62, 1913.) 



former case there is no evidence that serpentinization in 

 its formation is a necessary antecedent or accompaniment. 

 (See e. g. Pratt and Lewis 1905, pp. 112-119.) Even in 

 the well-watered districts of southern India or of the 

 southern end of the Appalachian Mountains, these 

 changes do not proceed far from the surface, but on the 



