104 RECONNAISSANCE IN NORTHERN ALASKA IN 1901. 



considered in connection with slickensiding and planes of weakness exhibited by 

 other specimens, shows thai ore deposition was followed by rock movement and 

 consequent crushing, which produced fractures, into which the barren stringers 

 were subsequently deposited by silica-charged solutions. 



The specimens al hand contain both wbite and yellow iron pyrites, which is mostly 

 fine-grained and normally occurs massive with the quartz, Imt in a few cases an 

 imperfect parallelism, or banding, apparently representing dispositional layers of 

 quartz and pyrites in varying amounts, is perceptible. 



The value of the ore rests in its auriferous content. At least three of the 

 larger veins are reported, from assays made for the owners iu San Francisco, to 

 carry from *40 to $90 per ton in gold." The gold seems to be contained, very finely 

 disseminated, in the pyrites, for so far as known no free gold is visible. None 

 was seen iu the specimens examined by the writer. 



Should these deposits prove to be of economic value, it is noteworthy that be- 

 sides being easily accessible by land, they can be approached at high water by way 

 of the Alatna River with flat-bottom steamboat to a point within 6 miles of the 

 locality, and at low water to a point within 20 miles. The region is reported to con- 

 tain a large amount of small timber having a stumpage of about 1 foot in diameter. 



COPPER. 



The only indications of copper seen in this northern country by the writer were 

 in detached fragments of quartz, apparently derived from veins, and carrying some 

 iron pyrites, copper pyrites, malachite, and a trace of bornite. Such specimens were 

 found sparingly in the river gravels on the upper Chandlar in 1899. * Some, seen in 

 the possession of prospectors, were reported to have been collected on Mineral Creek, 

 at the head of Chandlar Lake, on the west side. A ledge is also reported to have 

 been found on East Fork of the Chandlar, which assayed well in copper. But the 

 ore is not known to occur in quantities of commercial value. 



In the Koyukuk Basin the indications are much the same as above described, the 

 occurrences being on the upper waters or the tributaries heading in the limestone 

 mountains. The principal specimens seen by the writer during the recent work 

 consisted of waterworn fragments found in the John River gravels and derived appar- 

 ently from quartz veins. The}' contained some copper pyrites and a little bornite. 

 Similar specimens were seen in the hands of Kowak natives on John River. What is 

 supposed to be a vein of considerable size, containing iron and apparently copper 

 pyrites, was observed in a steep limestone cliff of the Skajit formation overlooking 

 the river, where no examination or collection could be made. 



a The Survey has just completed the assay of four of the above-described ore specimens, with the following results, in 

 ounces per ton: Specimen B, gold 0.05; silver none. Specimens C and D, gold, trace; silver, trace. Specimen F, gold 0.10; 

 silver, 0.08. These results are not promising. 



b Op. cit., p. 482. 



