8 



PROCEEDINGS OF THE NEW YORK MEETING 





I. 



II. 



III. 



IV. 



V. 



VI. 



VII. 



VIII. 



IX. 



Si02 



61. 3G 

 Undet. 

 1G.5G 

 3.44 

 2.93 

 Undet. 

 .85 

 4.5G 

 G.8G 

 1.30 

 I.5-) 

 traces. 



58.3G 

 1.49 



16.13 

 3.85 

 3.25 

 .6G 

 2.91 

 3.57 

 4.51 

 2.41 

 1.61 

 1.54 



57.38 

 2.22 



16.30 

 3.70 

 2. 66 

 1.70 

 1.61 

 5.12 

 3.58 

 2.29 

 1.08 

 2.66 



57.29 

 1.42 



19.93 

 2.95 

 3.39 

 .75 

 1.55 

 5.67 

 3.34 

 1.92 

 1.53 

 none. 



56.93 

 .98 



17.61 

 3.04 

 3.24 

 2.23 

 1.77 

 5.03 

 3.97 

 2.93 

 .74 

 1.45 



5G.3G 

 .83 



15.46 

 5.00 

 1.85 

 1.49 

 2.00 

 5.28 

 4.91 

 2.73 

 1.34 

 1.92 



55.77 

 .34 



16.38 

 4.27 

 4.17 

 Undet. 

 3.10 

 G.G6 

 3.65 

 2.37 

 2.36 

 1.58 



55.68 

 1.45 



17.09 

 5.2G 

 1.98 

 1.5G 

 2.23 

 5.05 

 2.83 

 1.95 

 1.50 

 2.97 



54.22 



TiOo 



1.65 



AI0O3 



16.69 



FegOQ 



3.63 



FeO 



3.39 



MnO 



1.43 



MgO 



CaO 



2.72 

 5.86 



NiioO 



4.82 



K2O 



2.20 



H..O 



1.55 



CO9 



2.53 







Specific gravity 



99.41 

 2.63 



100.29 

 2.G55 



100.30 

 2.745 



99.94 

 2.66 



99.72 

 2.70 



99.17 

 2.735 



100.65 

 2.745 



99.55 

 2.725 



100.69 

 2.695 



I. Hornblende-andesite, summit of southeast spur of Galena mountain, above Big 10 claim, 

 near Silverton, Colorado. 



II. Hornblende-andesite, tunnel of Dives claim, upper level, King Solomon mountain, near 

 Silverton, Colorado.^ 



III. Hornblende-andesite, west slope of Boulder mountain, ly, miles north of Silverton. 



IV. Hornl)lende-andesite, from Middleton, 6 miles northeast of Silverton, on east side of road. 



V. Hornblende-andesite, 30 feet from hanging wall of Big 10 vein, Galena mountain. 



VI. Hornblende-andesite, country rocks of Dives claim, upper level of King Solomon mountain. 



VII. Hornblende-andesite, Little Giant peak of King Solomon, slightly below summit toward 

 Cuningham gulch. 



VIII. Hornblende-andesite, summit of Little Giant peak of King Solomon mountain, about 

 14,000 feet above sealevel. 



IX. Hornblende-andesite, hanging wall of Big 10 vein (east side). Galena mountain, near Silver- 

 ton, Colorado. 



The analyses show at first glance that the rocks are of andesitic character, and 

 also that they are badly decomposed. All the rocks have a similar character, with 

 a tendency to form a series, ranging from acid to basic members. However, if the 

 CO2 were calculated to the remaining constituents, the basic end of the series 

 would not be so low. Nevertheless these rocks belong to the basic rather than to 

 the acid andesites. In the analyses the constant presence of considerable Ti02 

 and MnO is to be noted. The Ti02, as before mentioned, is probably to be found 

 in the magnetite. The fact that the microscope shows the presence of apatite in 

 small quantities will partially explain the fact that some of the analyses are too 

 low, as P.2O5 was not determined. The advanced stage of alteration of these rocks 

 will also explain other seeming irregularities in the analyses. In many cases the 

 rocks have undoubtedly been altered by the ore-bearing solutions which have de- 

 posited most of their material in the veins of the district. 



Conclusion 



The rocks in the neighborhood of Silverton, Colorado, comprised in the trian- 

 gular area bounded by Galena, King Solomon, and Boulder mountains are liorn- 



