604 abstracts: geology 



stocks of granite prophyry and quartz porphyry that may be geneti- 

 cally related to the mineralized quartz veins. The largest and most 

 continuous gold-bearing quartz veins that have been found are in the 

 basins of those streams whose placers have yielded the most gold. 

 This seems to be conclusive proof that the gold of the placer gravels 

 was derived, at least in large part, by the erosion of the larger quartz 

 veins that cut the schists. The local origin of the placer gold is also 

 confirmed by the appearance of the gold itself. 



In those portions of the region that were glaciated the erosion by 

 the ice was sufficiently severe to disturb or remove the greater part of 

 the preexisting gold placer deposits, so that any concentrated deposits 

 of gold that are now present are due to the erosion by streams since 

 the ice retreated. 



A fact that has notably influenced the gold placer deposits in many 

 valleys is the large volume of detrital material that has moved from the 

 valley walls down the slopes and out upon the stream gravel deposits 

 and the rapidity with which this movement takes place. 



R. W. Stone. 



GEOLOGY. — Tungsten minerals and deposits. Frank L. Hess. 

 U. S. Geological Survey Bulletin 652. Pp. 85, with maps, sections, 

 and illustrations. 1917. 



An attempt is made to gather into this bulletin the general facts 

 about tungsten, the minerals in which it is found, the kinds of deposits 

 from which these minerals are obtained, and other information, and to 

 show by illustrations, colored and uncolored, the appearance of typical 

 specimens of the various tungsten minerals. 



Tungsten deposits seem to be invariably in or associated with grani- 

 toid rocks, though they may be associated with their prophyritic facies, 

 and, so far as is known, only with the varieties that contain consider- 

 able quantities of free quartz, and usually if not always with the lighter- 

 colored members. 



Most of the tungsten deposits of the country are in the states that 

 lie in and west of the Rocky Mountains — South Dakota, Montana, 

 Colorado, New Mexico, Idaho, Utah, Arizona, Nevada, California, 

 Oregon, and Washington — all of which contain at least small deposits. 

 Wyoming is the only state in this whole great western area in which no 

 tungsten is known to have been found. R. W. Stone. 



