Vol. 4] Murgoci. — Classification of the Amphiboles. 



361 



Although my investigations have not been conducted accord- 

 ing to the plan mentioned above, I wish to present in the fol- 

 lowing pages the results obtained in the glaucophane series. The 

 rich material which I used in these investigations has been put 

 at my disposal by Professors J. Perrin Smith (Stanford Univer- 

 sity), Andrew C. Lawson (University of California), and Charles 

 Palache (Harvard University), to whom I wish in this place to 

 express my heartiest thanks. Especially in frequent consulta- 

 tions with Professor J. P. Smith, who has accumulated the rich- 

 est and most interesting collection of glaucophane and lawsonite 

 rocks, much light was thrown on the subject. Further, some 

 ideas have been generously suggested to us by Dr. A. C. Lane, 

 who several years ago made, but did not publish, some observa- 

 tions in this field. 



I. 



AMPHIBOLES OF THE GLAUCOPHANE SCHISTS. 



In the glaucophane schists and some other rocks from Cali- 

 fornia which I had the opportunity of investigating may be 

 distinguished many amphiboles which show a color and pleochro- 

 ism in blue, violet, or green more or less pronounced. Two or 

 more of these amphiboles may occur at once in the same rock and 

 slide, and often one single lamella has zones or patches of two 

 or even three amphiboles quite different from one another. Of 

 course the separation of one type for a detailed chemical and 

 physical investigation is almost impossible. Slight variations in 

 the properties of the same amphibole are general and obvious 

 under the microscope ; thus it is very difficult to determine the 

 chemical composition of one type, and if one has an analysis of 

 an amphibole separated from a given rock, one cannot always be 

 sure to what variety it would best correspond. 



The nomenclature and classification which it is sought to 

 establish here are made on the basis of the best analyses available, 

 together with an exhaustive determination of the optic properties 

 (under the microscope), and with a careful study of the litera- 

 ture on the minerals. I have distinguished : (gastaldite) glauco- 

 phane, crossite, crocidolite, rhodusite, karinthine soretite ( ?), Ian- 

 cite, actinolite, etc. Actinolite, karinthine, and glaucophane seem 



