ALASKA AND ITS MINERAL RESOURCES 155 



has become a well-established industry, and 'many large quartz 

 mills are running on the ore extracted from these veins. The 

 principal deposits of southeast Alaska are found in a belt some- 

 what over 100 miles in length on the seaward slope of the main- 

 land, reaching from Sumdum on the southeast past Juneau to 

 Berners bay near Seward on the northwest. This belt may be 

 also considered to include the deposits on Admiralty and other 

 interior islands. A second belt, further west, is represented by 

 the deposits on the western side of Baranof island, not far from 

 Sitka. The ores, though not always exceptionally rich, are 

 worked at a good profit because of the natural facilities of the 

 region for cheap reduction. The most notable instance of this 

 is tbe great Alaska-Treadwell mine, which has extracted over 

 seven million dollars 1 worth of gold from an ore carrying $3.20 

 a ton, which is worked at an average cost of $1.35. Such condi- 

 tions can not be expected to obtain in the interior. 



These deposits occur in metamorphic slates, diabases, and 

 granites, all similar to the rocks of the auriferous belt of Cali- 

 fornia, and probably, like those, they are of post-Jurassic age. 

 Owing to the dense covering of living and fallen forest trees in 

 this region, prospecting is extremely difficult, and it is probable 

 that future exploration will prove the extent of these gold belts 

 to be much greater than at present appears. The gold-bearing 

 beach sands from Lituya bay to Yakutat bay, along the west foot 

 of the St Elias range, and the placers at the head of Cook inlet, 

 around Turnagain arm and on the Kaknu river, may have been 

 derived from the wearing down of rocks of similar age and com- 

 position in the St Elias range and on the Kenai peninsula. 



At Uyak ba}^ on Kadiak island, gold deposits in slates are 

 being worked, and the gold-bearing beach sands of the western 

 end of that island and at Portage bay and the Ayakulik river on 

 the neighboring mainland are apparently derived from meta- 

 morphic slates associated with granite, so that it is possible that 

 these more recent gold-bearing rocks extend that far westward. 

 On Unga island, of the Shumagin group, still further west, gold 

 occurs in eruptive andesites of Tertiary age, and mines have been 

 opened on these deposits, the most important of which is the 

 Apollo, one of the most successful in the province. As the Alaska 

 peninsula and the Aleutian. islands are largely made up of recent 

 eruptive rocks, this is an important indication, showing the pos- 

 sibility of the occurrence of valuable deposits in such roeks. 



In the Yukon basin the gold, so far as known at present, is de- 



