696 W. N. Benson — Origin of Serpentine. 



The discussion now passed to the question whether 

 serpentines could be produced from any other rock than 

 peridotite. Both (1869) held that all non- aluminous 

 ferromagnesian minerals could pass into serpentine, and 

 that the process of change was the result of atmospheric 

 weathering. Weigand (1875) claimed that the serpen- 

 tines of the Rauenthal in the Vosges were derived from 

 non-aluminous hornblende, and described the lattice- 

 structure as evidence of this change. Professor Bonney 

 (1887) expressed his doubts concerning this conclusion, 

 and it was shown by Miss Eaisin (1897) to be in part 

 erroneous. Hussak (1882) described the knitted-struc- 

 ture of antigorite-serpentine as indicating its origin from 

 augite, studying the rocks from Windisch Matrei in the 

 Austrian Tyrol, formerly termed "serpentine-like rocks" 

 by Drasche (1871). Becke (1894) and Weinschenk 

 (1894), who studied the same occurrence, have shown 

 that antigorite could be derived from purely olivinic 

 rock, and that the lattice and knitted-structures of ser- 

 pentine could not be applied indiscriminately to deter- 

 mine the origin of serpentinized rocks. The general 

 unreliability of these structures in this connection has 

 been further emphasized by Bonney (1905, 1908). That 

 pyroxenes, both rhombic and monoclinic, and also amphi- 

 bole, may be changed into serpentine is, however, recog- 

 nized by him. 



Bonney had shown in 1877 the intrusive character of 

 the serpentine of the Lizard, confirming De la Beche's 

 view (1839) ; later he proved the Ayrshire serpentines 

 to be intrusive (Bonney 1878), though they had been held 

 to typify the interbedding of serpentine with slates, and 

 in the following year he confirmed the conclusions of 

 DelaBeche (1831) and Jervis (1860) concerning the intru- 

 sive character of the Ligurian serpentines (Bonney 

 1879). Nevertheless, the apparent interbedding of these 

 rocks with the sediments caused them to be considered 

 in some way different from normal igneous rocks. Tara- 

 melli (1884) and Dieulafait (1881) held that they were 

 chemical precipitates formed by the passage of hot 

 springs of alkaline silicates into a sea enriched in mag- 

 nesian salts; Stopanni (1880), Stefani (1876) and Issel 

 (1879) considered that they were submarine lavas, which 

 had been poured out over the Eocene sediments. This 

 view was supported by Pantanelli (1880), who described 



