NONMETALLIC DEPOSITS OF SOUTHEASTERN ALASKA. C 
The following table shows the value and produetion of this rock in the United States: 
Production of gypsum in United States, l ( J()J,.<i 
Grade. 
Crude 
Land plaster 
Plaster of Paris. 
Wall plaster 
Quantity 
(tons). 
56, 137 
70, 167 
274,672 
390, 668 
Value. 
$61,234 
142,490 
882,262 
1,698,339 
Average 
value 
per ton. 
SI. 09 
2.03 
3.21 
4.35 
o Mineral Resources U. S. for 1904, U. S. Geol. Survey, 1905, p. 1037. 
These average values represent the prices at which the various classes of product were 
sold at the mines and plaster plants, respectively. It can readily be seen that only exten- 
sive deposits situated favorably as regards mining and transportation can be worked with 
profit. Gypsum in sufficient quantity to warrant extensive development and extraction 
is known to occur at only one locality in southeastern Alaska. 
The Pacific Coast Gypsum Manufacturing Company owns claims on Gypsum Creek, at 
the head of Iyoukeen Cove, a small bay on the east shore of Chichagof Island. Here a 
small bluff of gypsum interbedded with cherty limestone was discovered I mile up the 
creek, and many tons of the rock have been quarried. Tests were made which proved 
this material to be an exceptionally pure gypsum and further investigations of the deposit 
have followed. Two tunnels 600 feet apart were driven on Gypsum No. 3 claim, and in 
each of these shafts 65 and 75 feet deep were sunk, almost entirely in gypsum. At the 
lower workings the gypsum bed appears to have an east-west strike and a dip of 60° S. 
Overlying it are strata of chert conglomerate, while beneath it beds of cherty limestone 
were exposed. From the bottom of the shaft the deposit is exposed by a crosscut for a 
width of 90 feet, entering to the north the hanging-wall conglomerate, but to the south 
penetrating a diabase dike. At the upper workings on the south side of the creek two 
beds of gypsum have been exposed in the shaft. These appear to lie relatively flat and 
are separated from each other by a stratum of conglomerate 17 feet thick. The upper 
bed is 40 feet thick, and at the time of the writer's visit the shaft entered the lower bed 
for a depth of 12 feet, but had not passed through it. The extent of the deposit was being 
investigated by drifts starting from the shaft and penetrating the beds in various directions. 
The gypsum and conglomerate beds rest unconformably on Upper Carboniferous lime- 
stones and are probably of early Mesozoic age, as are many of the gypsum deposits in 
the Western Stages. 
Developments on a large scale by this company are in progress, and a railroad 1 mile in 
length is in course of construction, which will transport the gypsum from the mine to 
bunkers of 1,000 tons capacity to be built on a wharf. The crude product will be loaded 
directly into hulks or barges and shipped to Puget Sound, where a plaster mill is to be built. 
COAL. 
The most extensive explorations for coal in southeastern Alaska have been at Kootz- 
nahoo Inlet and Murder Cove, on Admiralty Island,^ and Hamilton Bay, on Kupreanof 
Island. At these localities the coal-bearing formations are Tertiary in age and made up 
of conglomerate, sandstone, and shale. These beds are all more or less faulted and appear 
to occupy basins formed in the more ancient rock beds. The coal is with few exceptions 
an impure lignite and occurs in narrow seams of no commercial value. 
At Murder Cove explorations were made on a seam 5 feet thick located 2 miles from deep 
water. This deposit, which contains the best grade of coal in the region, proved to be of 
very limited extent and not worthy of further development. 
a Wright, C. W., A reconnaissance of Admiralty Island: Bull. U. S. Geol. Survey No. 287, 1906 (in 
press). 
