W. N. Benson — Origin of Serpentine. 717 



werk (1903) who has generously permitted this mention 

 of a feature in his slide not previously noted, and also his 

 concurrence in the interpretation here suggested. Sev- 

 eral slices of the serpentines of the Gross Venediger 

 Stock, Austrian Tyrol, described by Weinschenk (1894) 

 seemed to the writer to be capable of a similar inter- 

 pretation. They appeared to show the development of 

 secondary magnetite in mesh-like bands of minute grains, 

 between the residues of the olivine and pyroxene crystals, 

 but these have been slashed across by blades of antigorite 

 in the usual manner, while antigorite completely replaces 

 the first formed chrysotile. Professor "Weinschenk 

 verbally informed the writer that analogous features are 

 present in some of the serpentines of Wurlitz, near Hof , 

 in the Fitchelgebirge, but while kindly permitting the 

 publication of this suggestion, does not himself accept it. 

 Hence these cannot be cited as indubitable examples of 

 the change here suggested. 



This structural change in serpentine has apparently 

 been observed by Bonney (1908), for he remarks that, 

 while few of the antigorite serpentines studied by him 

 contain any residual olivine, in a few the matted antigo- 

 rite is traversed by tiny strings of opacite resembling 

 those in a serpentine formed from that mineral. 



With regard to the general question of the origin of 

 antigorite, a few words may be given. Weinschenk him- 

 self states that the formation of primary antigorite is 

 very rare ; and, though his hypothesis has been fre- 

 quently tested since it was announced, few instances 

 have been found which seemed to call for this explana- 

 tion. Krotov (1910) and Granagg (1906) have accepted 

 the hypothesis of the primary crystallization antigorite, 

 as best explaining the features of serpentines in the 

 Southern Urals and Carinthia, but reasons given in each 

 case, the former certainly in abstract only, do not seem 

 quite convincing. On the other hand, Bonney (1914) has 

 decisively rejected the hypothesis. After a study of 

 some of the original material from the Gross Venediger 

 Stock, by kind permission of Professor Weinschenk (who 

 has most clearly and fully described the features devel- 

 oped), the writer could not feel completely convinced of 

 the necessarily primary origin of the antigorite in the 

 very remarkable slides that he saw. He could not go 

 beyond the cautious comment of Harker (1897) that, 

 "though the reasons for regarding the antigorite as an 



