﻿690 PROF. T. a. BONNET AND MISS C. RAISIN ON THE [Nov. I905, 



33. The Microscopic Structure of Minerals forming Serpentine, 

 and their Relation to its History. By Prof. T. G. Bonnet, 

 Sc.D., LL.D., F.K.S., V.P.G.S., and Miss Catherine Raisin, 

 D.Sc. (Read June 7th, 1905.) 



[Plate XLV — Microscopic Kock-Sections.] 



Contents. 



Page 



I. Introduction , 690 



II. Serpentine from Olivine 691 



III. Amphibole 693 



IV. Orthorhonibic Pyroxenes 694 



V. Monoclinic Pyroxenes 696 



VI. Antigorite-Serpentine 699 



VII. The Sprechenstein Serpentines 701 



VIII. The Sattelspitz District 704 



IX. The Matrei Serpentine 705 



X. Other Alpine Serpentines 706 



XI. Slaty Serpentines 709 



XII. Serpentines from Japan 712 



XIII. Chemical Changes 712 



XIV. General Conclusions 713 



I. Introduction. 



Although so much has been written about serpentine during the 

 last thirty years, a few points, as we think, still require to be 

 cleared up. So we propose to describe in this paper, though it will 

 mean some repetition of details already in print, the changes by 

 which that mineral, or group of minerals, is produced from certain 

 magnesian or ferromagnesian silicates. One of us published his 

 first paper on this subject in the beginning of 1877, and since then 

 he has been able to do some field-work on the rock on an average 

 at least once a year. Of the specimens thus procured a number 

 have been sliced for microscopic study, and others acquired by 

 gift or purchase, so that his collection now includes about 180 1 

 sections of peridotites and serpentines, besides a large number 

 containing more or less altered single grains of the parent-minerals. 

 From the study of these, and of other specimens in the cabinets of 

 friends, the opinions expressed in this paper have been in- 

 dependently formed, and it would have been written half a dozen 

 years ago, if his arrangements had permitted him to visit certain 

 localities, concerning which, as he believed, incorrect statements 

 had been made. That task was kindly undertaken by the other 

 contributor to this paper, who, in the summer of 1904, supplied 

 the last link by visiting Sprechenstein and the Brenner district. 

 Prior to this she had made a special study of the serpentines of 



1 It contains, among others : from Cornwall 57 specimens, from Scotland 

 16 specimens, and from the Alps 43 specimens ; the remainder representing 

 various localities in Europe, Asia, Africa, North America, and Japan. 



