C. Palache — Occurrence of Olivine. 493 



Magnesite 1 



Brucite 4-34 



Serpentine 10*35 



] 6 • 1 6 



Deducting this 16'16 per cent alteration products from the 

 analysis and recalculating to 100 per cent, we obtain the fol- 

 lowing figures, which give a ratio almost exactly that of oli- 



vine. 



Theory for 

 olivine with 

 Mol. ratio Eatio Mg : Fe = 9 : 1 



SiO„ 41-58$ -688 1 41-00$ 



FeO 9-33 -130 ) 9-8 



MgO 48-94 1-223 1-355 1-97 49'2 



MnO -14 -002 



100-00 100-00 



In view of the discussion on a later page (p. 495) the absence 

 of fluorine is important. 



The vein containing the olivine is sharply defined in the en- 

 closing serpentine and is evidently a younger formation. We 

 have here apparently another case of the regeneration of olivine 

 in a rock mass which has undergone a general serpentiniza- 

 tion — a process previously recorded by Weinschenk* in serpen- 

 tine in the Tyrol and observed by the writerf in the peridotite 

 of Mine Hill, Cumberland, E. I. 



The curious appearance of these specimens of olivine embed- 

 ded in serpentine recalled the description of the above mentioned 

 hampshirite pseudomorphs as given by Emerson:}: ; it seems 

 to the writer, and his conclusion is wholly confirmed by Profes- 

 sor Emerson after seeing the specimens, that the close accord- 

 ance in general locality of Mr. Cowles' specimens and the orig- 

 inal hampshirite and the general similarity of the minerals, 

 save that in the single specimen of hampshirite studied by Pro- 

 fessor Emerson the olivine was wholly altered to serpentine and 

 brucite was not developed with it, point to the conclusion that 

 we have here a rediscovery of the long-lost locality of the pseu- 

 domorphs and final proof of their derivation from olivine. 



On the latter point it is necessary to refer to a recent paper 

 by Mr. A. D. Koe and Mr. A. L Parsons,§ in which the history 

 and nature of these pseudomorphs is discussed. 



* Beitrage zur Petrographie der ostlichen Centralalpen speciel des Gross- 

 venedigersstockes. Abh. Kgl. bayer. Akad. Wiss. II el. 1894, xviii, 651. 



f An occurrence soon to be described by Dr. C. H. Warren in a paper on 

 this interesting locality. 



{Emerson, B. K., Mmeralogical Lexicon, Bull. 126, U. S. G. S., pp. 92, 146. 



§ A Mineral Eesembling Meerschaum from the Serpentine Bange of Hamp- 

 den County, Mass., with Descriptions of Interesting Included Crystals, Bull. 

 Minnesota Acad. Sci. IV, No. 2, 1906, pp. 268, 276. 



