316 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [March 8, 



Blanket Creek and other Diggings. — Near to Blanket Creek, and 

 about five miles soutli from Sonora, I found the remains of a large 

 quartz-vein, resting apparently on the granite rock. It was about 

 20 feet long, 3 feet wide, and 3 feet high ; with decomposed 

 gneiss (the remains, probably, of its original matrix) lying against 

 each side. On examination I could not discover that it anywhere 

 penetrated the granite. There were no gold-diggings near, though 

 the place had been well tried, from which fact it might be argued, 

 that the gold had been removed (or at least the appreciable portions) 

 long before the quartz-vein was worn down to its granite bed ; and 

 this was the more remarkable, as the remains in question formed a 

 portion of one of the three great auriferous quartz-veins which traverse 

 California. It is the most eastern of the three (see Map and Section, 

 figs. 1 & 2), and passes by Sonora, which is considered the richest 

 district of the southern mines. 



Following the same line southward to Blanket Creek and Canaka 

 Creek, I observed that the metamorphic rocks are worn very low. 

 At one spot a few miners had discovered a deposit of gold in what 

 had been a deep chasm in the crystalline limestone ; but, with this 

 exception, no gold was found so high up these creeks : and in de- 

 scending, the first that was found in them was in large lumps, the finer 

 and lighter gold, in all probability, having been washed away. 



Coyote Creek. — At Coyote Creek, where I had worked for two 

 months, the rocks had suffered great displacement, possibly in con- 

 sequence of being in contact with a granite peak that rose high above 

 the surrounding metamorphic rocks. In one branch of this creek 

 that passed between the gneiss and limestone we frequently found 

 garnets. 



Sonora : workings in quartz-vein. — At Sonora I went to examine 

 a quartz-vein that was being worked for the gold it contained, and 

 was expected to prove rich. Its situation, on the side of a steep, 

 high hill, afforded facilities for running levels, and accordingly one 

 had been cut through the vein about 50 feet below the outcropping, 

 and a shaft had then been sunk to a considerable depth into the vein, 

 with the hope of finding it richer, but the gold found up to that time 

 was so minute as to require grinding and amalgamation to collect it. 

 The ravine below was very rich, and many large lumps were found 

 which must have fallen from that same vein. One piece that I saw 

 there weighed sixty ounces. See also p. 314. 



Murphy's Diggings. — New diggings having been discovered near 

 to Murphy's Camp, which were said to be in a new kind of ground, 

 I went to see the workings, and found them situated on a hill 

 formed of tertiary ? calcareous deposits (fig. 5). See also MoA-e/wwe 

 Hill Diggings, p. 319. 



The gold was found in a blue clay, or decomposed slate, mingled 

 with pebbles of quartz beneath the calcareous deposit. Some of the 

 miners had to sink 90 feet, and then found the auriferous earth in 

 what seemed to be an old creek or water-course. 



There are several of these hills in the immediate vicinity. One in 

 particular (which is, in fact, a part of this same hill) seems to retain 



