XJLAR 18

UNITED STATES DEPARTMENT OF THE 

INTERIOR J. A. Krug, Secretary.

GEOLOGICAL SURVEY W. E. Wrather, Director.

October 1947

NONMETALLIFEROUS DEPOSITS IN THE 

ALASKA RAILROAD BELT

By 

Gerald A. Waring

WASHINGTON, D. C.

UNITED STATES 

DEPARTMENT OP THE INTERIOR 

J. A. KRUG, Secretary

GEOLOGICAL SURVEY 

W. E. WRATHER, Director

CIRCULAR 18

NONMETALLIPEROUS DEPOSITS IN THE ALASKA RAILROAD BELT

By

Gerald A. Waring

WASHINGTON 

1947

CONTENTS

ILLUSTRATIONS

Figure 1. Index map showing location of nonmetalliferous

deposits in Alaska Railroad belt...................

2. Sketch map showing location of limestone ledges near 

Windy..............................................

Page

Introduction by George M. Flint, Jr................................ 3

Granite............................................................ 3

Occurrence in Alaska........................................... 3

Granite near Eklutna....................................... 3

Granite near Curry......................................... 3

Limestone ......................................'..................*. 5

Occurrence in Alaska........................................... 5

Limestone near Potter...................................... 5

Limestone near Windy....................................... 5

Limestone near Nenana...................................... 6

Limestone near Fox......................................... 6

Clay............................................................... 9

Clay on Healy and Lignite Creeks........................... 9

Clay at Government Hill, Anchorage......................... 9

Clay at Point Woronzof..................................... 9

Clay near Cantwell......................................... 9

Page

TABLES

Page 

Analyses of limestone from the Alaska Railroad belt...... 8

INTRODUCTION

In recent years the need for building materials in the Alaska Railroad 

belt has increased to many times the prewar demand, largely as a result of 

military and related construction. It is expected that this need not only 

will continue but will increase in the postwar period as a result of new 

construction.

Deposits of several types of nonmetallic minerals used in construction 

are known in the Railroad belt (see fig. 1),- but none has been developed on 

a commercial scale. This report is based largely on an investigation in 

1931 by G. A. Waring, who spent seven weeks examining nonmetalliferous 

deposits, other than coal, along the Railroad. Since that time the activities of the Geological Suvery in this area have been confined almost entirely to studies of metalliferous deposits and coal, and only a few brief 

examinations of nonmetalliferous deposits, incidental to other studies, 

have been made.

GRANITE 

Occurrence in Alaska

Granitic rocks underlie large areas in many parts of the mountain 

ranges of Alaska. On the Islands and adjacent mainland of southeastern 

Alaska a considerable part of the land area consists of granitic rocks. 

Similar rocks are present in the northeastern part of the Alaskan Peninsula, in various parts of the Alaska Range, in the mountains of the Seward 

Peninsula, and in the Yukon River basin. In the Kuskokwim River basin 

there are areas of granitic rocks, occurring chiefly as stocks and dikes. 

The central mass of the Talkeetna Mountains, in south-central Alaska, is 

largely granitic rock.

In spite of the abundance and widespread occurrence of granitic rocks 

in Alaska, the lack of local demand for building stone has prevented the 

development of a quarrying industry in most parts of the Territory.

Granite near Eklutna

Near Eklutna, about 9 miles south of Matanuska, a small mass of mediumgrained quartz diorite forms a group of low hills that are about a quarter 

of a mile in diameter and 100 feet in maximum height and lie about 1,000 

feet west of the railroad, on the shore of Knik Arm. The southern half 

of the deposit is owned by th.e Office of Indian Affairs and has been 

developed by the Alaska Railroad as a source of coarse riprap. The northern half of the deposit is on private land. The rock at this locality is 

generally massive, without gneissic structure or jointing, and is exceptionally fresh as a result of glacial scouring that removed all weathered rock.

Granite near Curry

A large body of granitic rock is exposed beside the Alaska Railroad 

in the canyon of the Susitna River about l£ miles south of Curry. The 

railroad bed was blasted out along the bluffs at the river's edge, and 

the granitic material is exposed along the railroad for about 200 yards. 

The granitic mass was intruded into black slate and schist. The intrusive 

is light gray medium-coarse grained, and even textured. The rock consists of quartz, plagioclase feldspar, white mica, and a small portion of 

dark minerals and is therefore a quartz diorite. A small amount of molybdenite is found along minor quartz veins and aplite dikes that traverse the 

mass. The quartz diorite has a slightly gneissic structure and cleaves 

readily into blocks. Although somewhat weathered superficially the rock is
184° 152

<£ i {PRINCE WILLIAM

50 100 MILES

FIG. I. Index map showing location of nonmetalliferous deposits 

in Alaska Railroad belt. A, Ekiutna (granite); B,Curry (granite); 

C, Potter (limestone); D, Windy (limestone); E, Nenana (limestone); 

F, Fox (limestone); G, Healy and Lignite Creeks (clay); H, Government Hill at Anchorage (clay); I, Point Woronzof (clay); J, Cantwell (clay).

4.
fresh and unaltered a few inches below the surface. The quartz dlorite is 

exposed in the canyon wall to an elevation of more than 600 feet above the 

railroad and for at least a half mile from the tracks.

For several years this quartz diorite was quarried by the Alaska Railroad for use as riprap. A siding was installed and the rock was quarried 

as needed. As quarrying progressed, however, the quarry face became too 

high for safe operations, the workings were abondoned, and riprap for the 

Alaska Railroad was obtained from the Eklutna deposit.

LIMESTONE 

Occurrence in Alaska

Deposits of limestone and marble are known in many parts of the Territory, the most extensive being in the islands of southeastern Alaska and 

the adjacent mainland. In 1912 and 1913 Burchard I/ examined 58 localities, 

8 of which had been opened as quarries. Since 1928, with the exception of 

the war years, the quarry of the Pacific Coast Cement Co. was operated on 

Dall Island. During 1946 the Alcoa Mining Co. carried on extensive development operations at Edna Bay on Kosciusko Island.

Large deposits of limestone are known in the Alaska Range and at 

several places in the interior of Alaska, but within the writer** knowledge 

they are too remote from transportation facilities to be of commercial 

interest.

Limestone near Potter

A prominent ledge of limestone lies half a mile northeast of the railroad, near Potter, 14 miles south of Anchorage, at the landward edge of the 

marsh land bordering Turnagaln Arm. The deposit consists of a lens in 

slate and schist. The limestone is about 20 feet thick, rises 25 feet 

above the marsh land, and juts out 50 feet from the hillside. It dips 

about 60° NW. Another lens, 6 to 8 feet thick, lies northwest of the first 

lens. The limestone may extend for several hundred feet into the hillside, 

and perhaps also for some distance In depth; ground water,however, would 

interfere with quarrying below the marsh level*

The property was patented as a mineral claim In July 1927, by C. R, 

and 3. F. Rhodes, of Anchorage. A few tons of the rock was quarried and 

burned to lime in a kiln at the site. This plant is now in ruins. The 

lime was used in plaster work in a few buildings in Anchorage. The analyses given in table 1 show the limestone to be unusually pure.

Such lenses of pure limestone are apparently not common in the altered 

sedimentary rocks of the district. Half a mile northwest of the quarry a 

broken mass of calcareous slate apparently forms another limy lens in the 

country rock. In the railroad cuts farther southeast along the shore of 

Turnagain Arm, a few lenses of limestone 1 to 2 inches thick were noticed. 

In the higher areas north and northeast of Potter, C. F. Park of the Geological Survey found small lenses and masses of limy shale.

Limestone near Windy

Limestone is present in a belt of highly metamorphosed rocks that 

crosses the Alaska Railroad in the vicinity of Windy, about 213 miles by

I/ Burchard, Ernest F., Marble resources of southeastern Alaska; with a section on 

the geography and geolojy, by Theodore Chapin: U. S. Geol. Survey Bull. 682, 1920.
rail.north of Anchorage. Several ledges of limestone are- exposed on the 

ridge extending 1^ to 2-| miles southwest of the station. The five most 

prominent ledges are shown in figure 2. Ledge A is at an elevation from 

800 to 900 feet higher than the railroad and half a mile north of it. 

The beds are nearly vertical in the enclosing slate and form a lens about 

300 feet long and 30 feet wide. The limestone is massive or thick-bedded, 

dark gray, and intricately fractured and traversed by a network of thin 

calcite veins. Ledge B, apparently a separate lens from Ledge A, is at an 

elevation 600 feet higher than the railroad-and forms an outcrop only a few 

square yards. Halfway between Ledge B and the railroad is a terrace of 

travertine or calcareous tufa, 100 yards wide. Between the terrace and the 

railroad the slope is covered by blocks of the tufa; tufa is still being 

deposited by the seepage water. Ledge C forms a prominent cliff on the 

crest of the ridge at an elevation 1,300 feet higher than the railroad. 

The limestone here is more massive, lighter in color, and less highly veined by calcite than the limestone in the lower ledges. Bedding is not 

evident, but presumably the limestone forms a lens in the nearly vertical 

slate. The limestone extends for a quarter of a mile along the strike of 

the slate and has a maximum width of 150 feet. Ledge D is at the eastern 

end of the higher part of the ridge where a thiclcness of about 100 feet of 

limestone at the base of a steep slope is exposed in three small cliffs. 

This limestone is similar to that of Ledges A and B but even more veined by 

calcite. Ledge E extends for a quarter of a mile along the south bank of 

Bain Creek, a small stream that empties into the Nenana River near Windy. 

The stream has cut against the ledge and formed cliffs in which is exposed 

a thickness of about 100 feet of limestone. The limestone at this locality 

is dark gray and intricately veined by calcite. Analyses of samples from 

the four principal ledges are given in table 1. One sample from Ledge A 

contains considerable magnesia, but the other sample from Ledge A, and that 

from Ledge C are usually pure limestones. The other two samples contain 

considerable silica.

The ledges described above apparently mark the eastern limit of limestone in this area. Abundant exposures to the east reveal only chert and 

greenstone. It is believed, however, that a more or less continuous belt 

of limestone may extend westward for at least 2 miles from these outcrops. 

The abundance of calcareous tufa on the slopes below the ledges suggests 

that limestone may underlie a larger area than the few outcrops indicate.

Limestone near Nenana

A lens of blue-gray limestone, about 400 feet long and 1 to 4 feet 

thick, enclosed in the Birch Creek schist, is exposed at mile 414.5 in a 

railroad cut on the north side of the Tanana River, opposite the Nenana 

depot. The limestone grades laterally into more siliceous schist. An 

analysis of the limestone (table 1) shows 2.1 percent of insoluble matter, 

probably silica, and a very low magnesia content.

Small lenses of white calcareous rock in the schist were observed at 

miles 416.6 and 416.9 and at other places, but none of these bodies is 

large enough to be of commerical importance.

Limestone near Pox

Pox is about 8 airline miles north-northeast of Fairbanks, at the 

junction of the Circle and Livengood Highways. At the base of a hillside 

about three-fourths of a mile southwest of Pox, and just north of the 

roadbed of the abandoned Tanana Valley Railroad, a lens of white finegrained limestone,- with a maximum thickness of about 15 feet, is exposed 

for 200 feet. Tests were made several years ago to determine the suitability of this stone for burning for lime. It was found to contain too
By G. A. Waring 

1931

FIG. 2rSKETCH MAP SHOWING LOCATION OF LIMESTONE

LEDGES NEAR WINDY, ALASKA

Contour interval 2OO feet
Analyses of limestone from the Air ska. Railroad be

(Maurice L. Sherp, U. S. Bureau of Mines, analyst)

Analysis numbe

1

Insoluble. ............................................ 

Silica (S102 )......................................... .HO

Iron and alumina (Fe20- + AlgO-j). . ..................... ' .HO

Magnesia (MgO). ....................................... ,1H

Lime (OaO). . .......................................... 5H. 70

Carbon dioxide ( C02 ) , calculated. ..................... 

Undetermined ( carbon dioxide and water) . .............. UH. 36

Loss on ignition. ..................................... 

100.00

2

.76

.72 

1.01 

96.56

.95

100.00

3

.H9 

.H2 

H.72

HH.17

99. H3

H

0.9

.9 

tr.

5H.H

!*.«

100.0

5

0.5

.7 

tr.

5H.7

H3.9

99.8

1

H

3

9

1. Limestone ne*r Potter, analyzed in May, 1926.

2. Lime burned from limestone neer Potter, enalyzed in May, 1926.

3. Limestone from Ledge A near Windy, analyzed in 1926.

H. Limestone from " A « » " 1931.

7 n n n -^ M n n

S. Limestone near Nenpne, analyzed in 1931*

9. Limestone near Fox, analyzed in 1931*
much magnesia to be of value for this purpose. An analysis of the rock is 

given in table 1.

Although the stone is considerably fractured at the surface, blocks 1 

to 2 feet in diameter probably could be obtained for use as building or 

monumental s tone.

CLAY 

Clay on Healy and Lignite Creeks

The coal-bearing formation of Tertiary age in the Nenana coal field 

includes numerous beds of clay and shale. Some of the clay and shale is 

suitable for the manufacture of brick and tile according to preliminary 

tests. One such bed, more than 100 feet thick, is exposed at the Suntrana 

coal mine on Healy Creek, 4 miles east of Healy, where it forms a prominent 

dark-brown band in the bluff, about 500 feet above the base of the formation. Similar brown shale has been traced for several miles along the 

upper course of Lignite Creek, about 4 miles north of Suntrana.

Samples of the thick bed of clay shale at Suntrana were collected in 

1923 by John A. Davis, engineer in charge of the station of the U. S. 

Bureau of Mines at Fairbanks, and sent to the Ceramic Experiment Station of 

the Bureau at Columbus, Ohio. The following data are from the report of 

the tests made there by E. E. .Pressler:

Clay from the upper 85 feet of the deposit proves to be the best. The 

lower part is too sandy to dry and burn satisfactorily. The clay works 

well in dies, and the drying behavior is satisfactory. It burns to a good 

body in the customary range of firing temperature for heavy clay wares. 

The total shrinkage is less than usual in a surface clay and only slightly 

above the average for shale. The clay is nearly free of lime, organic 

matter, and sulfur, which are objectionable in clays for heavy ware. The 

color of the ware when fired to high temperature is good. Some clays, that 

burn to a less pleasing color are used in the manufacture of face brick.

Clay at Government Hill, Anchorage

Interbedded in the unconsolidated sands and gravels that underlie 

Government Hill, north of the mouth of Ship Creek in Anchorage, is a bed 

of clay 10 feet or more thick. In 1928 the Alaska Railroad had this clay 

tested to determine its suitability for brickmaking. Several thousand 

bricks were made and used in local construction, but apparently they had 

not been burned sufficiently to withstand crumbling. Laboratory tests on 

small samples of the clay showed it to have small shrinkage, to burn well, 

and to have all the other qualities of a good brick clay.
Clay at Point Woronzof

A bed of dark-gray clay, very cohesive and plastic when wet, is 

exposed in low bluffs on the shore of Cook Inlet near Point Woronzof, 4 

miles west of Anchorage. The bed is at least 30 feet thick and is almost 

or completely free of sand grains. This clay and that at Government Hill 

probably were deposited in the tidal estuary, as they are similar to 

deposits of clay now forming on the wide mudflats that are exposed at low 

tide along Knik Arm. A purer clay probably can b0 obtained from Point 

Woronzof than from either the Government Hill.'or Suntrana localities, but 

all three places offer abundant material for local brickmaking.

Clay near Cantwell

In the railroad cut half a mile northeast of Cantwell Station (mile 

319.5), there is a small amount of white clay which is very plastic when 

wet. It is on the eastern border of a light-colored, felspathic porphyry 

dike 300 feet wide. This dike rock is "highly decomposed and locally has 

weathered into white clay. Only a few cubic feet of the clay was seen when 

the area was visited by the writer in July 1931, and it is very doubtful 

whether a deposit of commercial size is present. Analyses of the rock and 

the clay by Maurice L. Sharp, analyst of the U. 3. Bureau of Mines, 

are as follows:

ANALYSES OP PORPHYRY DIKE AND CLAY 

NEAR CANTWELL

Dike rock Clay derived from

_________________dike rock

Loss on ignition 10.2 7.3

Insoluble 76.9 88.4

Iron oxide and alumina (FegOs + AlgOs) 8.4 3.2

Lime (CaO) 3.4 0.7

Magnesia (MgO) 1.1 tr.

100709976

10