398 PROCEEDINGS OF THE CALIFORNIA 



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the kaoline is as perfectly porphyritic in its texture and appearance as in any 

 portion of the mass, while between the two is every grade of passage from the 

 one to the other -the country rock being neither distinctly porphyritic in text- 

 ure, nor chiefly feldspathic in composition. I am strongly inclined to think, 

 therefore, in spite of its peculiar and distinctive character, that this porphyritic 

 mass is but a local result of the metamorphism of sedimentary strata, which, 

 in many portions of this region, seems to have been as varied in character as it 

 has been high in degree. 



The degradation of such formations as this at Quail Hill, has undoubtedly 

 furnished some of the placer gold of the region ; but the evidence does not by 

 any means justify us in supposing that it has furnished the whole of it. Gopher 

 Gulch, which runs at the foot of Quail Hill, and its branches, for a mile above 

 this point, or nearly to the summit of the Gopher Range, and hundreds of feet 

 above the level of the Quail Hill formation, were in early days rich in placer 

 gold, much of which was very coarse. Other gulches in the vicinity have also 

 furnished more or less gold high up towards the summit of the range. More- 

 over, the quartz veins, which here and there occur in the hard metamorphic 

 rock, are known, some of them at least, to contain gold, and such have probably 

 played their part in the formation of the placers. 



I have already mentioned the fact of the prominent association of the prec- 

 ious metals with ores of copper at the Quail Hill mine ; but this fact derives 

 still further interest from what follows. As far as my observations have extend- 

 ed in Calaveras County, and also at Whisky Hill, in Placer County, wherever 

 gold and silver have yet been found in paying quantities in the decomposed rock 

 formation, there also, or close at hand, are found the oxidized ores of copper, 

 carbonates and silicates ; and conversely, I have nowhere seen oxidized ores of 

 copper in this decomposed rock which were not, comparatively at least, rich in 

 gold and silver. It is true that sufficient developments have not yet been made 

 to enable us to state whether this is the general fact or not. It is possible that 

 the association of these ores may be to a certain extent accidental ; but it is not 

 unlikely that it may be otherwise ; — and at all events this is a point well worthy 

 of attention and further investigation. 



As this finishes my remarks upon the " calico rock " formation, I will close 

 by simply mentioning a point relating to the lower country of Calaveras Coun- 

 ty, that I have not yet seen publicly noticed elsewhere. The low, rolling hills 

 which form the eastern border of the San Joaquin plain between the Stanislaus 

 and Calaveras Rivers, contain extensive beds of horizontally stratified material, 

 which is probably sedimentary-volcanic in origin. The color of these beds is 

 usually varying shades of gray. They contain no pebbles, so far as I have 

 seen ; they generally crumble easily, and resemble in appearance a friable sand- 

 stone. But their grain or grit, which is pretty fine, is also quite clean and 

 sharp as well as hard, and rough-polishes rapidly the hardest steel when rubbed 

 upon it. 



These beds are of considerable thickness, and cover many square miles of 

 country. Their stratification has evidently not been disturbed since they were 

 deposited, though they have been largely eroded. The frequeut flat tops of the 



