University of- Calif orn id Publications. 



[Geology 



page 



Aegyrine 



Caleite and Aragonite 

 Manganese Dioxide ... 



363 

 363 

 363 

 364 

 366 

 368 

 369 

 370 

 371 

 371 



Country in which the Veins Formed 



Sequence of Events 



Distribution of Minerals in Veins 



Relation to the Serpentine 



General Discussion 



Recent Papers 



Supplementary Notes 



INTRODUCTION. 



A brief announcement of the recently discovered mineral 

 benitoite was made in a preliminary paper issued in July, 1907. 1 

 The purpose of the present paper is to give a general de- 

 scription of the nature of the occurrence and a more complete 

 account of the major minerals than was possible at that time. 

 The writer is indebted to Mr. R. W. Dallas, vice-president and 

 manager, and Mr. Thomas Hayes, superintendent of the Dallas 

 Mining Company for permission to visit the mine and for as- 

 sistance in obtaining material for study ; and' to Shreve and 

 Company of Han Francisco and in particular Mr. G. Eacret, 

 head of the diamond department, for gem and other material 

 and assistance in many ways during the progress of the work. 



Since the public announcement of the discovery of this 

 beautiful gem mineral many efforts have been made to find new 

 occurrences of it, but so far without success. The writer has, 

 in connection with another problem, examined several hundred 

 occurrences of analogous deposits, and several other geologists 

 who have worked in the Coast Ranges of California have taken 



i Benitoite, a New California Gem Mineral, by George Davis Louder- 

 back, with Chemical Analysis by Walter C. Blasdale. Univ. Calif. Publ. 

 Bull. Dept. Geol., V, No. 9 (July, 1907), pp. 149-153. Announcement was 

 then made that new material hail been received and a more complete report 

 would follow. The main points of this latter report were presented before 

 the Geological Society of America at its Albuquerque meeting in Decem- 

 ber, 1907. Various causes have contributed to the delay in publication of 

 this material, in particular a severe illness which has kept the writer from 

 the field of activity for the greater part of a year. In returning now 

 to the completion of the manuscript for publication it is found that re- 

 cently certain phases of the work have been duplicated by others. The 

 results are presented here, however, as they were originally worked out by 

 the writer and his eo-worker and reference made to the other articles at the 

 end of the paper. 



