48 ALASKAN MINERAL RESOURCES IN 1904. [bull. 259. 
Because of the illness of the senior author the preparation of this 
paper has fallen chiefly to the junior author, who has abstracted the 
notes of the former and presents the following conclusions. 
The purpose of this paper is to give a brief summary of the eco- 
nomic developments which have been made during the past few years 
in southeastern Alaska. A more complete discussion of investiga- 
tions, accompanied by maps of the region, is in preparation and will 
be published later. 
The total gold production from southeastern Alaska for 1904, 
excluding that of the Treadwell group of mines, is estimated to aggre- 
gate $275,000. The yield of the Treadwell mines will be approxi- 
mately $3,000,000. The production of silver will not be greater than 
$30,000, and, excepting small shipments for smelter tests, that of cop- 
per has been nil. 
GEOLOGY. 
To make clear the descriptions of the ore deposits, the general geo- 
logic character of the Alexander Archipelago will be briefly described, 
after which the several mining districts will be treated in turn. 
STRUCTURE. 
The distribution of the coast formations in wide, extensive belts, all 
striking in a general northwest-southeast direction with relatively 
steep dips, facilitates the geologic mapping to a great degree. The 
arrangement of the sedimentary rocks points to simple structure, and 
though folds a thousand feet or more in width are prominent among 
the islands, a duplication of the beds on a large scale has not been 
observed. Numerous intrusions of igneous rocks, essentially of granite, 
diorite, and gabbro, have caused a displacement and metamorphism of 
the sedimentary beds, rendering difficult a grouping into continuous 
series. The lack of fossils in many of the strata likewise prevents at 
the present time a definite correlation of the formations. 
DISTRIBUTION OF ROCKS. 
The main mountain mass between the international boundary and tide 
water is composed of a light-gray eruptive rock. This rock in general 
i esemblesa granite and is usually so named, but microscopic examination 
proves it to be a granodiorite or a quartz-diorite of coarse crystalline 
texture. Southwest of this Coast Range invasion are gneissoid rocks 
and highly metamorphic schists, interstratified with narrow belts of 
marble. Adjacent to these and bordering the coast of the mainland 
are argillaceous slates, more or less carbonaceous, including limestones,] 
and these again are followed by extensive belts of more or less schis- 
tose greenstone. 
