1922] Vaughan: Geology of San Bernardino Mountains 409 



ORE DEPOSITS 



In the late sixties the search for gold in California led a few 

 prospectors far from the better known fields of the Sierra Nevada 

 and some eventually found their way to the San Bernardino Moun- 

 tains. Gold was found in the gravels of Holcomb Valley and resulted 

 in a sudden inrush of miners for its exploitation. It is said that more 

 than $7,000,000 worth of the precious metal was taken out, and that 

 this small valley once had a population of more than three thousand. 

 It is now practically deserted. 



Naturally the enthusiasm of these pioneers led them to search for 

 the original source of the gold and many tunnels were driven into the 

 surrounding hills; but, although gold can be found in many places, 

 no real mines were discovered. Only a few of the prospects were 

 examined by the writer. A small quartz vein in the granite on the 

 southeast side of Union Flat contains small amounts of pyrite and 

 galena and also a little gold. In Van Dusen Canon gold is associated 

 with pyrite, chalcopyrite, galena, and sphalerite near a contact between 

 granite and limestone. 



On the SE y 4 , Sec. 30, T. 3 N, R, 1 E, gold is found in quartz veins 

 with pyrite, galena, and sphalerite. The country rock is limestone 

 striking N 60° W and dipping 40° SW, and is cut by granitic dikes 

 with which the veins are associated. In one case a fine-grained horn- 

 blende-diorite dike nine feet thick follows the bedding of the lime- 

 stone a short distance and then dips more steeply, thus cutting diag- 

 onally across it. Along the under side of this dike is a quartz-galena 

 vein about six inches thick, the galena being in the central part. The 

 gold is often found in some of the veins in calcite as pellets weighing 

 as much as two grams. In contrast with most California gold, that 

 found in this region, both in the veins and in the gravels, is remark- 

 ably free from silver, seldom containing as much as 2 per cent. 



In Wild Rose Canon there has been considerable mineralization 

 along a granitic dike. Wollastonite and especially tremolite are com- 

 mon, some fibers of the latter attaining a length of more than four 

 inches. Other minerals present are pyrite, chalcopyrite, and a little 

 gold. Some malachite and azurite are found in the shallow oxidized 

 zone. 



