370 BULLETIN 131, UNITED STATES NATIONAL MUSEUM 



kaolinization. Kaolin, in fact, is a product not ordinarily found in 

 the mineral veins and talc occurs still more rarely. 



This altered granite, together with the ore or gangue occurring 

 in seams or veins through it, constitute what the miners term a 

 ''ledge" and "ledge matter. " This may be many feet wide, and the 

 paying ore may, and in fact does usually, form only a small portion 

 of the width of the ledge matter. The altered country rock, though 

 often well filled with pyrite and arsenopyrite, is ordinarily very poor, 

 containing at most $1 or $2 in gold. 



While sericite has for some years been recognized as an important 

 mineral of metalliferous ore deposits and its essential identity with 

 muscovite has been sufficiently demonstrated, there are, in the 

 literature very few records of thorough chemical investigation of 

 material from metalliferous veins, especially upon samples of demon- 

 strated homogenity and freedom from extraneous impurities. A 

 considerable amount of excellent material being available a sample 

 from the Carroll-Driscoll claim in Boise County was analyzed. The 

 description, which has previously been published, 780 is here repeated. 

 The specimens were collected by Edward L. Jones of the United 

 States Geological Survey, whose description has furnished the data 

 on the occurrence of the mineral. 79 



The Carroll-Driscoll group comprises 14 claims which extend in a 

 northeasterly direction from the end lines of the Gold Hill group 

 to Garden Valley Pass. The property was worked in the early days 

 and many thousand dollars' worth of gold was produced from surface 

 workings and by sluicing disintegrated veins on the Ivanhoe and 

 Capital claims at the head of California Gulch. The principal 

 development work on this group consists of two tunnels, 178 feet 

 apart, on the Ivanhoe claim. The upper tunnel, which is several 

 hundred feet long, is now partly caved. It is a shallow drift on the 

 vein which strikes N. 30 E and dips steeply east. Considerable ore 

 has been produced but the amount is not definitely known. The 

 ore consists of veinlets of massive pyrite and a little quartz which 

 carry free gold. The country rock is granite. 



The lower tunnel is driven on a course N. 60° W. for 1,450 feet. 

 It intersects a shear zone 135 feet wide, which contains several 

 sulphide veins in zones of more intense shearing. These veins 

 trend from N. 30° E. to north and dip steeply east. The largest 

 vein is near the hanging wall of the main shear zone, and its width 

 ranges from 3 to 12 feet. The zone is further explored by a drift on 

 its hanging wall and by short crosscuts driven to the main vein. 

 The shear zone contains an abundant flow of water which, together 



780 Earl V. Shannon. Notes on the mineralogy of three gouge clays from precious metal veins. Proc. 

 U. S. Nat. Mus., vol. 62, art. 15, 1922. 



n Edward L. Jones, jr. Lode mining in the quartsburg and Grimes Pass porphyry belt, Boise Basin, 

 Idaho. U. S. Geol. Survey, Bull. 640, p. 104, 1916. 



