44 ALASKAN MINERAL RESOURCES IN 1906. 
nary bituminous coal, to lignites of various character. Many of the 
coal beds are of great thickness, especially where the coal is of high 
carbonization, but unfortunately the high grade of coal and the great 
thickness of the beds are as a rule accompanied by an irregularity of 
the geologic structure that is unfavorable to mining conditions. 
The Pacific coast coals are in general favorably situated for shipment, 
and in this respect, as in the character of some of the coal, offer possi- 
bilities for a larger, more regular, and wider market than any of the 
other Alaska coals. 
INTERIOR REGION. 
The interior region, which is here defined to include the valleys of 
Copper and Yukon rivers and their tributaries, contains Cretaceous 
bituminous coal on the lower Yukon and Tertiary lignite and sub- 
bituminous coal on the upper Yukon and in the Tanana, Koyukuk, 
and Copper river basins. None of this coal is suitable for export, 
but it may be of considerable importance as local fuel. 
BERING SEA AND ARCTIC SLOPE. 
The coal of the Bering Sea and Arctic slope region includes great 
range in geologic age and great variety in character. Coal is present 
in the Carboniferous, Jurassic, Cretaceous, and Tertiary. The Cape 
Lisburne coal includes Carboniferous semibituminous and Jurassic 
bituminous, and in the Colville basin Cretaceous bituminous coal and 
Tertiary lignite are present. The other coal, as far as is now known 
(except the Wainwright Inlet coal, which is Jurassic), is all lignite 
of Tertiary age. 
It is not likely that any of this coal is of immediate value for other 
than local use. The high-grade coal at Cape Lisburne may find an 
extensive market at Nome, but the shipping problems are serious. 
The other coal is of such character that its market must be restricted 
to local regions in which the cost of better imported coal is high. It 
may be of extreme importance and of great value in local operations, 
but it is not good enough to ship very far from the mines. 
CHARACTKi; OF THE COAL. 
The character of the coal in the Alaska fields has been stated in the 
previously published descriptions of the various fields and has been 
referred to in the preceding pages. A detailed discussion of this sub- 
ject is consequently not necessary here. The following table is a 
summary of all the analyses of Alaska coal which have been made for 
the Geological Survey, and shows approximately the character and 
value of the coal from the known areas: 
