LINDGRKN.] 



VEINS OF NEAL MINING DISTRICT. 



701 



these again by the granite-porphyry. It is probable that all of them 

 antedate the veins. Remains of a glassy rhyolite are found on Three 

 Point Mountain and the ridges northward. 



THE VEINS. 



The Neal district was visited in October, 1896, but only two days 

 could be devoted to it, and I therefore gladly availed myself of the 

 offer of the following notes by Mr. F. D. Howe, superintendent of 

 the Hidden Treasure mine, who is thoroughly familiar with the dis- 

 trict and with whose statements my own observations in the principal 

 mines fully agree. Credit for many of the above data regarding the 

 dikes of the district is also due to Mr. Howe. 



The veins of the district have the common N. 70 to 83 E. trend and the same 

 general dip to the south, and for form may be referred to three classes: First, veins 

 filling larger fault fissures, on which are located the principal mines; second, veins 

 along the minor shearing planes of the granite, more or less irregular, but gen- 

 erally carrying high-grade 

 ore; and third, veins of a 

 hard white quartz, called by 

 the miners "bull quartz," 

 carrying no values. 



The veins on the fault 

 fissures are often displaced 

 by faults of a north-south 

 trend, which occurred sub- 

 seqtient to the vein filling. 

 The position of the north- 

 south faults is often shown 

 on the surface by gulches of 

 greater or less size. The dip F IG . 65. Cross section of vein in the Neal mining district, 

 is to the south, ranging from 



30 to 54, somewhat steeper than that of the foliation. The granite of the foot 

 wall for some little distance away from the vein has suffered a decomposition of 

 its mica, is harder, and is cut by cross jointing planes, in which are thin seams 

 of a talcose mineral, giving it a blocky appearance. Garnets occur on this side of 

 the fissure and may be of secondary origin. On the hanging- wall side the granite 

 is darker, and the main joints follow the fissure and no cross jointing appears. 

 On this side only appear the oxides of manganese. Beyond the sheeting or joint- 

 ing of this side there is a zone of structureless granite (fig. 65). 



The vein filling is separated from the walls by thin seams, but in places the 

 mineralization extends into both walls, in which case the gold in the walls is 

 coarser than that of the vein proper. 



The vein matter consists of quartz, sulphides, and partly replaced country rock. 

 The ordinary structure is, next the hanging wall, a clear quartz, more or less 

 honeycombed and stained by the oxidation of the iron pyrites; next, a zone of 

 replaced country rock, granite or one of the dark rocks described above, carry- 

 ing much pyrite and other sulphides. 



Pyrite often occurs in the dike rock in detached kidneys and sometimes as par- 

 tial replacements. The width of the veins varies from 2 to 13 feet. The gold 

 occurs free in the quartz; partially free in the pyrites. It varies from microscopic 



