Geology

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Vol. 5]	Louderback.—Benitoite.	333

particular notice of minerals and veins occurring in similar geologic surroundings without seeing either of the more characteristic minerals of this particular deposit. And it is not because these minerals are difficult to see, for on the contrary they are striking in appearance. They do not occur as microscopic forms, but always in distinctly visible crystals commonly of fairly good size. It would appear reasonable to conclude that the minerals have not been simply overlooked, but that they are really very restricted in their occurrence and are due to a special and unusual set of conditions—a peculiar variation, as the writer believes, of a type of geologic activity of rather general occurrence along the Coast Ranges. The locality and general geological surroundings therefore assume considerable interest. THE LOCALITY. The only locality of benitoite known at present lies in San Benito County, California, near the Fresno County line, on a short tributary of the San Benito River which joins the latter near its source. It is on the west side of the Diablo Range and not far from its summit line, and about twenty-five miles in a straight' line (probably thirty-five miles by road) north of Coalinga, where the mining company that owns and works the property has its headquarters and from which it ships its supplies.² Its geographical position is represented on the index map, plate 27. The mine is located on section 25, township 18 south, range 12 east, Mount Diablo base and meridian.

2 It has been found very difficult to determine just who is the discoverer of this interesting deposit. Different individuals have laid claim to this title and a comparison of their various accounts shows that the ambition to be so called has led to misrepresentations of the facts. As the writer has already given names in his preliminary report and has found that the original accounts given him are not entirely correct, he feels that a further statement is due. Mr. J. M. Couch, a prospector of Coalinga, grubstaked by Mr. Dallas, had in December found some deposits that seemed to need further examination, and Mr. Dallas induced Mr. L. B. Hawkins of Los Angeles to accompany Couch into the mountains for that purpose. While out to examine some copper prospects they happened on the benitoite deposit and each claims to be responsible for the discovery. Having no idea of the nature of the material, they took some back to town for further enlightenment. At first the idea, expressed by some '' expert'' in Los Angeles, prevailed that the material was volcanic glass and of no value. Later some stones w^Tere cut in San Francisco, the lapidary believing that they were sapphires, and for some time the property was known as the Sapphire Mine.

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