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PEOF. T. G. BONNET ON ANTIGORITE 



[May 1908, 



9. On Antigorite and the Yal Antigoeio, ivith Notes on other 

 Serpentines containing that Mineral. By Prof. T. G. 

 Bonnet, Sc.D., LL.D., P.E.S., E.G.S. (Read February 5tli, 



1908.) 



Contents. 



Page 



I. The Original Specimen and the Yal Antigorio 152 



II. Other Antigorite-Serpentines 158 



III. Note on Bowenite 169 



I. The Original Specimen and the Yal Antigorio. 



The exact locality of the type-specimen of antigorite is apparent!}' 

 unknown, as I found when preparing my portion of the paper by 

 Miss Baisin and myself on the minerals forming serpentine.^ 

 E. Schweizer, who first described it,- states that the specimen 

 (5 inches long, 2 inches wide, and 2 inches thick) was in the 

 collection of D. P. Wiser of Zurich, who had bought it the year 

 before 



' von einem mit Mineralien handelnden Bauer aus Oberwallis, nach dessen 

 Aussage diese Substanz in kleineren und grosseren, bisweilen einen Fuss 

 langen, diinnschiefrigen Platten im Antigoriothale bei Domo d'Ossola gefunden 

 werden soil ' ; 



and was unable to obtain any more precise information from the man. 

 It has been subsequently noticed,^ among others, by Des Cloizeaux, 



1 Quart. Journ. Geol. Soc. vol. Ixi (1905) p. 690. 



^ Pogg, Ann. vol. xlix (1840) p. 595. He says that it is ' wenig glanzend,' 

 semi-transparent in thin plates to transparent in the thinnest, with H=2*5 

 and ^.Gr. = 2*622, and gives two analyses which he afterwards withdrew as 

 incorrect, the amount of water having been much underestimated. 



^ In the following works :— (1) Kenngott, ' Mitth. an Kenngott Uebers. Min. 

 Forsch.' 1856-57, p. 72, asserts that antigorite can be traced into ordinary 

 serpentine, (2) G. J. Brush, Amer. Journ. Sci. ser. 2, vol. xxiv (1857) p. 128, 

 gives a correct analysis, saying that it proves antigorite to be one of the slaty 

 varieties of serpentine. (3) A. Des Cloizeaux, 'Man. Min.' vol. i (1862) p. 110. 

 (4) Kallmann, ' Elemente der J\lin.' 1877, p. 579, says that many include it 

 with serpentine. (5) Dr. E. Hussak, Tschermak's Min. & Petr. Mitth. n. s. 

 vol. v (1883) p. 65, refers antigorite to a pre-existing pyroxene, describing 

 and analysing specimens from Sprechenstein, etc. (6) Prof. A. Cathrein, Neues 

 Jahrb. vol. i (1887) p. 151, adds interesting particulars of Tyrol serpentines, 

 saying that those from augitic rock do not contain chromite or picotite, and 

 quotes Kispatic as saying (Mitth. aus d. K. Ungar. Geol. Anst. vol. viii, 1886-90, 

 p. 198) that antigorite had come from a hornblende. (7) MM. A. Michel-Levy & 

 A. Lacroix, ' Les Min. des Eoches ' (1888) p. 278, quote Prof. Rosenbusch as 

 attributing ordinary serpentine to the transformation of peridote and amphibole, 

 the leafy forms (bastite and antigorite) to the same pyroxenes, especially the 

 enstatite-family. (8) Prof. F. Zirkel, ' Lehrbuch der Petrogr.' 2nd ed. vol. iii 

 (1894) p. 384. (9) Prof. G. Tschermak, ' Lehrbiich der Min.' 5th ed. (1897) 

 p. 514. (10) Prof. H. Eosenbusch, ' Elem. der Gesteiulehre ' (1898) p. 524. 

 (11) Prof. Carl Hintze, ' Min.' vol. ii (1897) p. 765, clearly connects antigorite 

 with pressure. (12) M. A. Michel-Levy, Comptes Eendus, vol. cvi (1888) 

 p. 779, gives, with other minerals, antigorite du Valais, orthorhombic, 

 lengthening or flattening parallel to gS extinction with it 0°, optical sign -ve. 

 (13) The optical properties of antigorite from the ' Yal d'Antigorio ' are 

 mentioned also by Klein, Neues Jahrb. vol. ii (1895) p. 127. 



