Geology

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	INTRODUCTION. A brief announcement of the recently discovered mineral benitoite was made in a preliminary paper issued in July, 1907.¹The purpose of the present paper is to give a general description 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 assistance in obtaining material for study; and to Shreve and Company of San 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

	ι 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 had 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 December, 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 recently 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 co-worker and reference made to the other articles at the end of the paper.

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