Dolomite Deposit 

Near Marble 

Stevens 

County 

Washington

By CHARLES DEISS

A CONTRIBUTION TO ECONOMIC GEOLOGY

GEOLOGICAL SURVEY BULLETIN 1027-C

A study of the geologic structure and 

petrology of a dolomite deposit

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1955
UNITED STATES DEPARTMENT OF THE INTERIOR 

Douglas McKay, Secretary

GEOLOGICAL SURVEY 

W. E. Wrather, Director

For sale by the Superintendent of Documents, U. S. Government Printing Office 

Washington 25, D. C.
CONTENTS

	Page 

Abstract..-_ __________-_______-__-_-_______--_____---__-_-----____ 119

Introduction. _____________________________________________________ 120

Location of deposit-_--__-________-_-___--________-_-_____---____-- 120

Sedimentary rocks.________________________________________________ 121

Northport limestone- __--_--______--_-________-_-_______-._____ 122

Glacial drift... __________-________-__-___________--__---_-._ 122

Glacial lake deposits.__________________________________________ 123

[gneous rocks.___-_-__--__-_-_---_-___--_----__---__---._-_-__---_ 125

Lamprophyre dikes.____________--___-____-__----___-_----.__-- 125

Petrography of the dike rocks.-.__________-________----_-___ 126

Economic significance of the dikes___________________________ 128

Geologic structure.________________________________________________ 128

Faults ----------------------------------------------------- 129

Joints.-.-___-.__----_---_---__----__-_._-___-------_. 129

Structures in the quarry face.___________________________________ 130

Dolomite deposit-___-___---____-__--_.._---__--__---__-____-_-_---_ 130

Lithology of the dolomite...------._____________________________ 130

Breccia zones.________-_____-____-______-_--_____--_-__-__ 132

Chemical analyses.__---___-_________________________________-^ 132

Lithologic section and position of selected samples _________________ 132

Silica and other impurities.--_---______-_-_----_______-___-.__-_ 135

Origin of the dolomite._________________________________________ 138

Mining conditions and methods. _____-_____-_-____-____-___-___-___- 139

Quarry operations.__-__---_--_--__-__--__--___-__.___---__-_-- 140

Crushing and screening.______________ __________________________ 140

Production ___.___--____-__-____-_-________-_-_________--____-___- 140

Selected bibliography. _____________________________________________ 141

ILLUSTRATIONS

Page 

PLATE 14. Geologic map of dolomite deposits near Marble, Stevens

County, Wash____________________________________ In pocket

15. Structure sections of dolomite deposits near Marble....- In pocket

FIGURE 28. Index map showing location of dolomite deposit.___________ 121

29. Southeast side of dolomite deposit-__-__--________-_____._ 124

30. Locations of igneous rock specimens and analyzed dolomite

samples. _____________________________________________ 127

31. Central part of quarry face._____________________________ 131

32. Continuous white quartz vein on intersecting joints.-------- 136

33. Irregularly intersecting vuggy quartz veins in dark-gray

dolomite___________________________________________ 136

34. White quartz vein enclosing angular fragments of dolomite. _ 137

35. Angular nodules of white quartz in dull-gray dolomite..-____ 137

36. Large vein of white quartz,._____________________________ 138

37. Buff-colored quartz surrounding leached fragments of dolomite breccia_ _______________________________________ 139

in
IV CONTENTS

TABLES

Page 

TABLE!. Chemical analyses of dolomite samples l-35_________________ 133

2. Chemical analyses of dolomite samples 36-43----------------- 133
A CONTRIBUTION TO ECONOMIC GEOLOGY

DOLOMITE DEPOSIT NEAR MARBLE, STEVENS COUNTY

WASHINGTON

BY CHARLES DEISS

ABSTRACT

The dolomite deposit 2 miles east of Marble in the northern part of Stevens 

County, Wash., was studied in detail during short periods in 1942, 1943, 

and 1944 by geologists of the U. S. Geological Survey. The deposit constitutes 

an isolated hill that trends northeast, is partly covered by glacial drift, and is 

surrounded by glacial lake sands, silts, and gravels. The dolomite is part of 

the Northport limestone, which is tentatively assigned to the Cambrian and 

is overlain by the Mission argillite of Weaver (1920), the youngest formation 

in the Stevens series of Weaver (1920).

The deposit is on the southeast limb of the Northport anticlinorium. The rock 

is strongly jointed and is broken by at least six dip-slip(?) normal faults that 

are found in two sets. The older set strikes N. 55°-60° E. and dips 66°-78° NW.; 

the younger set strikes N. 10°-23° E. and dips 72°-80° W., offsetting the older set. 

At least 9 lamprophyre dikes, whose outcrops range from 4 to 25 feet in width 

and from 20 to 180 feet in length, have intruded along faults or along joints 

parallel to faults. Contact minerals or other impurities are not associated with 

the dikes.

The dolomite is commonly light gray, but at a few places it is banded dark 

gray. The dolomite is finely crystalline, thick bedded, and massive; and certain 

areas within it contain quartz in the form of veins, nodules, vuggy masses, and 

breccia cement. The silica probably was deposited by hydrothermal solutions 

and, in some places, is sufficiently abundant to prevent commercial exploitation 

of the dolomite. The dolomite is a bedded sedimentary deposit and dolomitization probably occurred at, or shortly following, the time of deposition. This 

is indicated by the lack of characteristics typical of hydrothermal replacement: 

deposits.

The deposit is readily accessible for open-pit mining. Analyses of the ore 

shipped and the amount of quartz observable in the outcrops suggest that the 

impurities in the deposit average more than 2% percent.

From the time the quarry was opened, in April 1943, till November 1943 an 

average of about 19,500 tons of ore per month was shipped to Spokane, Wash. 

In mid-November 1943 production was cut to less than half of the previous 

tonnage. Mining activity ceased by January 1, 1945.

119
120 CONTRIBUTIONS TO ECONOMIC GEOLOGY

INTRODUCTION

The dolomite deposit near Marble was studied in order to make an 

accurate geologic and topographic map showing the distribution of 

the dolomite, and of other rocks and impurities in the deposit. The 

dolomite was studied also to determine the geologic structures that 

might affect exploitation of the deposit. As dolomite is a relatively 

new ore of magnesium, knowledge gained from this intensive geologic 

study may prove useful in establishing criteria for evaluating 

unworked deposits.

The first geologic field work near Marble was done in 1942 by J. M. 

Hill and B. N. Webber, of the Electro Metallurgical Co. The U. S. 

Geological Survey, as a part of its search in the West for dolomite 

that might be used as a source of magnesium, began fieldwork near 

Marble on September 17, 1942, when a stratigraphic section (p. 134) 

was measured and 35 rock samples (p. 134) were collected. Between 

October 4 and November 22, 1943, the area was mapped on a scale 

of 1:2,400. The deposit was revisited briefly by the writer in 

September 1944.

G. E. Ericksen assisted the writer throughout the fieldwork and 

aided in the preparation of the maps and structure sections. F. W. 

Sandoz, quarry superintendent, Spokane Portland Cement Co., furnished a private map of the property and information concerning mining, milling, and production. E. H. Mangan, general superintendent 

(1942-44), Spokane Works, Electro Metallurgical Co., granted 

permission to study the deposit. The late E. S. Leaver of the U. S. 

Bureau of Mines, Reno, Nev., supervised the chemical analysis of 

samples 1 to 35. Harold E. Culver, supervisor, Washington Division 

of Geology, visited the deposit while the fieldwork was in progress 

and made helpful suggestions concerning glacial deposits in the region.

The dolomite deposit is on the southeast side of the' Columbia River 

and is 2 miles 1ST. 80° E. of Marble, a station on the Great Northern 

Railroad (fig. 28). The nearest town is Northport, Wash. A railroad 

spur, formerly owned by the Defense Plant Corp., extends from the 

screening plant at the deposit (pi. 14) to the Great Northern track 

south of Marble.

The dolomite forms an isolated hill which trends N. 55° E. The 

hill is 3,560 feet long, is 1,340 feet wide at the widest part, was sculptured by glacial ice, and is partly covered by till and stratified drift. 

The highest point of the hill (altitude 2,077 feet) is 285 feet above the 

flat to the south and 335 feet above the flat to the north (pi. 14). Most 

of the deposit is in the NE% sec. 27, T. 39 N., R, 39 E., Willamette
DOLOMITE DEPOSIT NEAR MARBLE, WASHINGTON 121

na'io'

INDEX MAP OF WASHINGTON SHOWING LOCATION 

OF AREA COVERED BY LARGER MAP

118° 10' neoo' 117" 50' II7°40' 117*30'

FIGURE 28. Index map showing location of dolomite deposit.

meridian, in the northern part of Stevens County, 10 miles south of 

the Canadian boundary and about 35 miles west of the Idaho boundary.

SEDIMENTARY ROCKS

Dolomite is the only sedimentary rock exposed in the map area 

except Pleistocene glacial deposits. The dolomite is within the belt 

of metamorphosed limestone and argillite, 6 to 8 miles wide, that 

extends from Northport 16 miles southwestward to Bossburg, Wash. 

Weaver (1920, p. 75-77) tentatively assigned the dolomite to the 

Northport limestone and named the argillite Mission argillite (p. 72- 

75). In his summary of the formations Weaver gave 3,000 and 12,000
122 CONTRIBUTIONS TO ECONOMIC GEOLOGY

feet, respectively, for the thicknesses of the Northport limestone and 

Mission argillite. He placed the formations in the upper part of his 

Stevens series (Weaver, 1920, pi. 1) and assigned them doubtfully to 

the Carboniferous. In his discussion of the lithology of the Northport, Weaver wrote: "The Northport limestone is in reality interbedded with the Mission argillite but as a stratigraphic unit it is so 

distinct that it has been mapped as a separate formation." As 

Weaver's Mission argillite does not crop out in or near the dolomite 

deposit, it will not be discussed in this report.

NORTHPORT LIMESTONE 

According to Weaver, the Northport limestone crops out along the

valley of the Columbia River in a belt 2i/£ miles wide' that extends 

from the mouth of Kettle River northeastward nearly to the Canadian 

boundary. The dolomite deposit is within this belt and is part of 

the Northport limestone. Weaver (1920, p. 76) described the formation as follows :

Prevailingly, it is a massive fine-grained white limestone which in places is 

dolomitic. South of Northport, on both sides of the Columbia River, the rock 

forms large areas of the surface geology and is typically massive and possesses 

a pure white color which sometimes passes to a light gray. It is usually finely 

crystalline but occasionally becomes rather coarse and shows stratification 

planes:

Much of the formation is metamorphosed limestone, but it probably 

contains more dolomite than is implied by Weaver's description.

The dolomite deposit is in the lower, thicker unit (main mass) of 

the Northport limestone shown on Weaver's (1920, pi. 1, sec. A-B) 

structure section. Until detailed stratigraphic work is done on the 

upper three formations of Weaver's Stevens series, the name 

Northport limestone should be restricted to this lower unit. The name 

is used in the restricted sense in this report. Weaver's map and structure section indicate that the Northport limestone underlies (rather 

than is interbedded with) his Mission argillite and may be the 

same as the Clugston limestone of Weaver (1920) which crops out 

7 miles southeast of the Marble dolomite deposit.

Weaver (1920, p. 50 and pi. 1) doubtfully assigned the upper formations of the Stevens series to the late Paleozoic, possibly of Carboniferous age. Fossils are unknown from these formations; but because 

the Northport limestone is similar lithologically to part of the Metaline 

limestone (Park and Cannon, 1943, p. 17-19), and because the 

Metaline has yielded Middle Cambrian fossils, the restricted Northport limestone tentatively is assigned to the Middle Cambrian(?).

GLACIAL DRIFT

The northern part of Stevens County was covered by the Columbia 

River valley lobe of the Cordi Reran ice sheet during the Pleistocene.
DOLOMITE DEPOSIT NEAR MARBLE, WASHINGTON 123

The evidence for and the effects of glaciation in the valley of the 

Columbia River near the dolomite deposit have been competently discussed by Flint (1936, p. 1869-71,1874-75). Erratics, patches of till, 

stratified drift, glacial striae on the bedrock, and ice-cut cliffs show 

conclusively that the dolomite deposit and the surrounding region 

were covered by glacial ice.

Glacial drift covers more than a fourth of the dolomite ridge and 

constitutes most, if not all, of the overburden on the deposit. In 

mining, the drift is removed by pushing most of it aside with bulldozers and by putting the remainder through the screening plant with 

the dolomite the till is discarded as part of the fines. About 200 

feet north of the present quarry (fig. 31) the drift is much thicker 

and more widespread than at the quarry site.

The shape and probably the size of the dolomite outcrop are the 

results of scour by ice (pi. 15) and of deposition of sands, silts, and 

gravels by glacial melt Avaters as the ice stagnated. In general, the 

till occurs on the dolomite hill, and the stratified deposits form the 

surrounding flat. The glacial drift is distributed irregularly over 

the hill, and much of it is confined to a wide irregular band that extends across the summit of the hill from the northeast side to the 

southwest edge (pi. 14). The till in this band conceals most of the 

faults mapped and may conceal extensions .of the dikes. In addition 

to the main bands of drift, many isolated patches, 5 to 300 feet in 

length, are irregularly distributed over the hill.

In most of the smaller isolated patches the till is probably less than 

10 feet thick, but in the larger areas it is as much as 25 feet thick 

and may be 50 feet thick. The till consists principally of soil particles mixed with some boulder clay and silt; and it contains many 

rounded and subangular boulders of quartzite, argillite, gneiss, and 

granite. Stratified silt and sand are mixed in some places with the 

till, and talus merges with and partly covers it in places near the 

base of the hill.

GLACIAL LAKE DEPOSITS

The valley flat surrounding the dolomite deposit consists of interstratified sands, silts, and gravels (fig. 29) deposited in ice-dammed 

lakes that were formed by melt waters of glaciers of Wisconsin 

age. Sediments thus deposited are present along the sides of most 

of the main valleys in northeastern Washington and are well developed in the valley of the Columbia River near Marble. Flint 

(1936,p. 1854) suggested:

Most of these bodies of [stratified] drift accumulated in entrants off the 

major valleys, when the valleys were filled with ice, and the entrants carried 

streams and lakes that were held to high local base-levels, and acted as catchment 

338680 55 2
124 CONTRIBUTIONS TO ECONOMIC GEOLOGY
DOLOMITE DEPOSIT NEAR MARBLE, WASHINGTON 125

basins for waste contributed chiefly from short tributary streams and from tbe 

adjacent slopes.

The unconsolidated sediments that underlie the rolling flat surrounding the dolomite h ill may have been desposited in an ice-dammed 

lake in late Wisconsin time by a stream in the valley of Onion Creek 

(fiff-28).

In the new railroad cut near the limestone plant, southeast of the 

dolomite deposit, the following section is exposed:

Feet

Sand and silt, slightly weathered in upper part___________ 0.33 to 2.0 

Silt and sand, buft'-tan, fine-grained- _._ _ 4.5 to 5.5 

Mud, black, extremely carbonaceous; some lumps appear to be very

dirty lignite_________________________________ .17 to .5 

Gravel and sand, interbedded lenses; stratified but generally not well

sorted. Some lenses of nearly pure sand_____________ 12.0 to 14.0

Total__________________________________ 17.0 to 22.0

The surface of the valley flat surrounding the dolomite hill is gently 

rolling and has a maximum relief of 82 feet within the area mapped. 

The flat between the railroad spur and the southeast edge of the hill 

ranges from 1,790 to 1,800 feet in altitude (pi. 14). Northwest of the 

hill the altitude ranges from 1,718 to 1,780 feet, the low point being 

near the north bulge of the hill. Between the isolated dolomite knob 

(pi. 14) and the southeast corner of the main hill, a block of ice 

rested while the sediments accumulated around it. The melting of 

this ice block allowed the sands and silts deposited against and over 

it to collapse, forming an elongate depression (fosse?) in the valley 

flat between the end of the railroad and the hill.

Flint (1936, p. 1875) suggested that the stratified deposits along 

the upper valley of the Columbia Eiver are younger than the Nespelem 

silt (Parclee, 1918, p. 28), which is a fine-grained facies of the main 

outwash fill in eastern Washington. In the small area studied by 

the writer, the lake beds certainly appear to be the youngest Pleistocene deposits, having been laid down during the last melting stage 

of the youngest Wisconsin glacier. The few isolated mounds of 

gravel and the erratics on the lake beds near the east end of the hill 

probably were ice-rafted into the lake or else represent englacial 

material dropped as the stagnating ice melted.

IGNEOUS ROCKS

LAMPROPHYRE DIKES

The Loon Lake granite (Weaver, 1920, pi. 1), exposed 2 miles 

east of the dolomite deposit, does not intrude the dolomite nor does 

it seem to have any bearing on the origin or composition of the deposit. 

Lamprophyre dikes are the only igneous rocks in the deposit.
126 CONTRIBUTIONS TO ECONOMIC GEOLOGY

The dolomite is intruded by at least nine dikes of medium-grained 

trachytic lamprophyre, which are irregularly distributed throughout 

the dolomite hill but are more numerous along its northwest side 

(pi. 1). Most of the dikes probably intruded along the younger faults 

or along joint planes parallel to them, and all except two strike between N. 12° and 30° E. and dip between 72° and 80° NW. Of the 

two aberrant dikes, one strikes N. 25° W., and the other, which intruded along the eastern fault of the older set (pi. 15, sec. C-C'}, 

strikes N. 55° E.

Outcrops of the dikes range from 4 to 25 feet, in width and from 

20 to 180 feet in length, and the largest are near the northeast end 

of the dolomite hill. Several of the dikes are irregularly ovoid in 

shape and are more like plugs than dikes. All except one are partly 

covered with till or talus. The most striking characteristics of the 

dikes are their apparent uniformity of mineral composition and grain 

size, their orientation parallel to the faults, and the presence in them 

of xenoliths. Neither contact alteration of the dolomite nor chilled 

zones in the dikes are apparent. Webber has written about contact 

relations in a private report: "The lamprophyre dikes have had no 

appreciable effect on the mass of dolomite. Contact action is confined 

to a thin, less than 1 inch, plate of epidote developed on the walls of 

the dikes."

The two dikes at the northwest and west ends of the dolomite hill 

contain xenoliths of quartzite and gneiss. The inclusions are angular 

and rounded pebbles of quartzite, '<% to 6^2 inches long and 14 to 3 

inches wide. One angular fragment of gneiss, 2 inches long and 2y2 

inches wide, was seen in the dike at the west end of the hill (fig. 30, 

sample 11). The contacts between the xenoliths and the lamprophyre 

are sharp. Possibly some silica was absorbed by the magma, but the 

quartzite fragments examined megascopically do not appear to be 

altered.

The source of the quartzite xenoliths may have been the Colville 

quartzite, which is reported to underlie the Clugston limestone of 

Weaver in northeastern Washington (Weaver, 1920, p. 68-71). The 

nearest outcrop of gneiss is the Orient gneiss of Weaver (192'0), 

possibly pre-Cambrian, along the Kettle River, 14 miles west of the 

dolomite deposit. The xenoliths afford little evidence of the distance 

that they were carried by the magmas.

PETROGRAPHY OF THE DIKE ROCKS

The following discussion of the petrography of the igneous rocks 

was excerpted from an unpublished report by R. L. Smith, who studied 

the rock specimens and thin sections in the laboratories of the U. S. 

Geological Survey. The encircled numerals 1 to 11 on the location
DOLOMITE DEPOSIT NEAR MARBLE, WASHINGTON 127

T.39N.. R.39E. Willamette Meridian Sec. 22 Sec.23

EXPLANATION

Lamprophyre dike or plug 

Numbers referred to in text

Fault 

Outline of hill

Line of traverse of lithologic 

section and position of 

analyzed dolomite sample

Sec.26

Geology and topography by Charles Deiss.assisted 

by G. E. Ericksen; surveyed in 1943-44___

FIGDKK 30. Locations of igneous rock specimens and analyzed dolomite samples.

map (fig. 30) indicate the dikes from which the respective samples 

were taken. Smith says:

The eleven igneous rock specimens have been classified as trachytic lainprophyres. They may, however, be segregated into three distinct groups.

A. The first group, which includes nos. 1, 2, 3, and 4 (fig. 30), is characterized 

by phenocrysts of labradorite and augite, and large phenocrysts of a dark 

red-brown biotite. The groundrnass consists of plagioclase, which is probably 

sodic-audesine, a large quantity of greenish brown biotite occurring in thin 

slivers, augite, and a considerable amount of interstitial quartz and orthoclase. 

Apatite and magnetite are abundant accessory minerals. The nature of the 

quartz and orthoclase suggests that they crystallized out later than the other 

minerals.

B. The second group, which includes nos. 5, 6, 7, and 8 (fig. 30), is characterized by its rather uniformly fine-grained texture and by abundant prismatic 

crystals of hornblende in the groundmass. In addition to hornblende, the 

groundrnass consists of sodic-plagioclase, either oligoclase or sodic-andesine, 

biotite, augite, a fair amount of interstitial quartz and orthoclase, and accessory apatite and magnetite. A few phenocrysts of biotite and augite are present. 

This group does not contain the combination of two types of biotite present in 

the first and third groups.

3386SO 55 3
128 CONTRIBUTIONS TO ECONOMIC GEOLOGY

C. The third group, which includes nos. 10, 11, and probably no. 9 (fig. 30), 

is characterized by augite and two kinds of biotite, and differs from the first 

group in that the feldspar is more alkalic, the plagioclase phenocrysts are absent, 

and more interstitial quartz is present. Nos. 10 and 11, which are almost 

identical, are more coarsely crystalline than any of the other rocks. Apatite 

and magnetite are present as accessories. No. 9 (fig. 30) differs from the other 

two in this group in that it contains no large pheuocrysts of biotite, but contains 

more augite.

Smith states that the rocks in all three groups have to some extent 

been altered. His report describes also the secondary minerals found 

in the samples.

ECONOMIC SIGNIFICANCE OF THE DIKES

The dikes apparently brought in little, if any, of the silica found 

in the dolomite. Their economic effect would be to increase the cost 

of selective quarrying and the cost of disposing of dike rock. However, differences in color and texture would make separation from 

the dolomite easy. None of the dikes is within the block outlined for 

mining by the Electro Metallurgical Co.

GEOLOGIC STRUCTURE

The dolomite is part of the southeast limb of a large anticlinorium 

that extends northeastward along the valley of the Columbia Kiver 

from Marble to beyond Northport, Wash. Weaver (1920, p. Ill) 

named the fold the Northport anticline and described it as follows:

The Northport limestones and the Mission argillites exposed along the valley 

of Columbia River form an anticline whose axis trends approximately parallel 

to the general course of the river. On the northwestern side of the river the 

dip is prevailingly to the northwest except where there have been local disturbances. On the eastern side of the river the dip is usually to the southeast 

but in places it is nearly flat. Apparently the fold is a very shallow anticline 

which has been so deeply eroded that the argillites overlying the Northport 

limestones have been removed. Faults whose positions have not been determined 

seem to obscure the general structure. This fold is referred to in this report 

as the Northport anticline.

Weaver's map (1920, pi. 1) suggests that the anticlinal axis strikes 

N. 50° E. The "Northport anticline" probably is an open asymmetric 

anticlinorimn, broken by many small strike and oblique normal faults.

The most obvious geologic structures within the dolomite deposit 

are joints, which are much more numerous and more easily recognizable than the bedding planes. Slight movement along many of these 

joints doubtless accomplished much adjustment within the major fold. 

Local folds were not observed; but two sets of normal faults, on which 

the displacement probably was not great, cut the dolomite.
DOLOMITE DEPOSIT NEAR MARBLE. WASHINGTON 129 

FAULTS

The dolomite hill is broken by at least six normal dip-slip or obliqueslip faults belonging to two westward-dipping sets (pis. 14, 15). 

The presence and position of these faults, which are covered most 

of their length with glacial drift or rock mantle, were deduced from 

field observations and from a study of aerial photographs of the 

deposit. As the dolomite in the deposit is nearly homogeneous, the 

faults will not affect the reserves and probably will not affect quarrying to any marked extent.

The faults in the first or older set trend nearly parallel.to the 

strike of the beds, are -subparallel to each other, and are broken 

by younger faults. Measurements on joint surfaces adjacent to the 

fault zones suggest that the older faults strike N. 55°-60° E. and dip 

66°-T8° NW. Because bedding planes are obscured and marker beds 

are absent in the nearly uniform mass of dolomite, the amount of 

movement along the faults is unknown (pi. 15), although the throw 

is apparently 50 to 100 feet on each fault. The block on the northwest side of each fault is downthrown in relation to the block on the 

east, and each may have been rotated slightly.

The younger oblique dip-slip normal faults (pi. 14) strike 1ST. 10°- 

23° E. and dip 72°-SO° W. The older faults are offset 80 to 200 feet; 

this suggests that the movement on the younger faults may have been 

greater than movement on the older ones.

Most of the dikes are on, or are subparallel to, the younger faults, 

indicating that the intrusions occurred after the older faults were 

formed and at the same time or slightly later than the younger faults. 

All the faults probably were formed when the compressi ve stresses that 

produced the ISTorthport anticlinorium relaxed.

JOINTS

The dolomite is broken by many joints which may be divided into 

five sets of high-angle and two sets of low-angle joints. The five 

high-angle sets (1) strike northeast and dip northwest subparallel 

to the older set of faults, (2) strike northeast and dip southeast, 

(3) strike north and dip west, (4) strike northwest and dip southwest, 

and (5) strike northwest and dip northeast. The two low-angle sets 

(1) strike northwest and dip northeast, and (2) strike northwest and 

dip southwest. The high-angle joints range in dip from less than 60° 

to more than 80°. Most of the joints are curved and readings taken 

on different parts of a joint surface may show a variation of 15° 

to 25°.

The most prominent joints are subparallel to the older set of faults 

(pi. 14), strike K 45°-59° E., and dip 65°-T4° NW. Although some 

of the joints that strike northeast clip southeast, most dip northwest
130 CONTRIBUTIONS TO ECONOMIC GEOLOGY

and form conspicuous clip-si ope cliffs on the northwest side of the 

hill. The southeastward-dipping joints probably were produced by 

stresses normal to the fault surfaces and, therefore, may be tension 

fractures.

The joints parallel to the younger set of faults are less conspicuous 

than those parallel to the older faults, and they constitute a system 

composed of three sets. The first set strikes 1ST. l°-5° E. and dips 

62°-82° W.; the second set strikes N. 10°-17° W. and dips 62°-80° 

SW.; the third set strikes N. 30°-38° W. and dips 60°-84° NE.

The joints in the dolomite deposit are important because they may 

have been the paths of ingress for solutions that deposited the silica, 

and because they greatly facilitate quarrying operations.

STRUCTURES IN THE QUARRY FACE

The quarry face (fig. 31) exhibits several eastward-dipping, intersecting, curved fault surfaces. The largest one is very curved and 

exposes a dome-shaped footwall. The fault surface strikes N. 30°-50° 

E., dips 40°-50° SE., and exhibits large grooves 2 to 4 feet wide that 

are secondarily grooved. On natural outcrops such striae would be 

interpreted as glacial in origin, but here they imply that the movement 

on this fault was horizontal. The surface is also slightly slickensided. Most of the other small faults also are curved (fig. 31), as 

are many of the joints exposed in the quarry face. A prominent 

set of joints strikes N. 22° E. and dips 60° NW.

The dome-shaped fault may have been formed during the early 

compressive stage of diastrophism, and the rest of the structures may 

have developed during a later tensional stage. The intensive jointing and faulting exhibited in the quarry face probably extend throughout most of the hill.

DOLOMITE DEPOSIT

The dolomite deposit is an isolated hill surrounded by a rolling flat 

of glacial lake sands, silts, and gravels (fig. 29). The mountain southeast of the flat and the hill to the north are composed of limestone and 

some dolomitic limestone. The dolomite hill, therefore, appears to 

be an isolated body within the Northport limestone. The lithologic 

relations of the dolomite to the limestone cannot be observed because 

of the surrounding cover. Studies of aerial photographs of the region 

suggest that the dolomite is slightly offset from, but has the same 

general strike as, the limestone on the opposite side of valley of the 

Onion Creek and is in the same part of the formation.

LITHOLOGY OF THE DOLOMITE

The dolomite is white gray, pale bluish gray, faint buff gray, and 

dove gray, and large areas are irregularly marked and banded dark
DOLOMITE DEPOSIT NEAR MARBLE, WASHINGTON 131
132 CONTRIBUTIONS TO ECONOMIC GEOLOGY

gray. Weathered surfaces are generally lighter in color than freshly 

fractured surfaces. The dark dolomite ranges from black gray to 

dull gray and at most places is marked with irregular light-gray spots, 

stringers, and masses. The small light-gray spots cause a conspicuous 

mottling, and in places are so numerous and small that they give the 

rock a coarse salt-and-pepper appearance. Some of the dark bands 

are parallel to the dolomite beds, but many cut across them irregularly. 

The dolomite is dense and hard, and is generally finely crystalline 

to microcrystalline. Some of the light-gray dolomite is slightly vitreous on fresh fractures. A few of the darker beds are sugary. Some 

of the. white masses in the dark areas are coarse grained, the crystals 

being as much as three-sixteenths of an inch long. In a few places, 

usually in association with vuggy quartz veins, the dolomite is stained 

buff tan (weathered limonite), and a red stain (impure hematite) 

marks certain breccia zones. Metamorphism has obliterated many of 

the bedding planes, which probably were obscure and widely spaced 

originally. Consequently, most of the exposed dolomite appears massive or imbedded. On the northeast end of the ridge the dolomite contains a few thin wavy siliceous bands, parallel to the bedding, which 

may represent metamorphosed shale partings. If so, they are the 

only clastic sedimentary rocks observed in the deposit. No beds of 

limestone and only three veins of coarsely crystalline calcite were 

found.

BRECCIA ZONES

Short breccia zones, 6 to 36 inches wide, are irregularly distributed 

in the dolomite. Two kinds of breccia are present. The more abundant type consists of angular fragments of dolomite cemented in a 

matrix of white or buff quartz (fig. 37). The other type is composed 

of subangular and a few slightly rounded fragments of light- and 

dark-gray dolomite cemented in quartz.

CHEMICAL ANALYSES

The chemical composition of the dolomite is shown in tables 1 and 2. 

Samples 1 to 35 are of rock taken from different beds in the measured 

section (p. 134). Their exact location on the deposit is shown on the 

map (fig. 30). Samples 36 to 39 are of crushed dolomite in grades 1 

to 3 and fines; samples 40 and 41 are chip samples taken from the 

quarry face and along the upper bench of the quarry; samples 42 and 

43 are chip samples taken across the strike of the beds in the southern 

and northern parts of the deposit.

LITHOLOGIC SECTION AND POSITION OF SELECTED SAMPLES

The following incomplete section gives details of the lithology of 

the dolomite and of the stratigraphic position of the analyzed samples
DOLOMITE DEPOSIT NEAR MARBLE, WASHINGTON 133

TATU.E 1. Chemical analyses (in percent) of dolomite samples 1-35 

[Analyst, E. S. Leaver]

No.

1

2

3

4

5

0

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

20

27

28

29

30

31

32

33

34

35

Ignition 

loss

40. 1

45.8

40.2

46.3

46.0

47.0

45.8

46.4

44.5

45.8

' 46.6

46.4

46.3

4(i.7

45.7

47.0

47.1

46.8

46.7

46.9

45.5

44.8

46.6

40.4

46.0

37.0

40.2

45.7

45.8

46.9

46.9

46.6

46.5

46.0

46.0

Insolubles

(Si02)

1.0

1.7

.6

1.4

2.0

.7

2.6

1.5

4.4

1.9

.5

1.3

1.4

.6

2.7

.5

.5

1.0

1.4

.6

3.0

4.5

1.0

1.7

.7

19.6

.6

1.2

2.6

.8

.0

.7

.9

1.0

1.0

KzCh

1.1

.8

.7

1.0

1.2

.7

1.1

.5

' 1.3

1.2

.7

.7

.5

.8

.4

1.0

.4

.4

.4

.3

.6

.6

.5

..7

.4

.0

.5

.0

.0

.3

.5

.3

.3

.4

.5

CaO

30.0

29.6

29.9

30.2

29.8

30.4

29.7

29.9

28.8

29.0

30.3

30.4

30. 0

30.2

29.7

30. 3

30.4

30.1

30.1

30.1

29.5

28.8

30.0

29.9

30.0

24.1

30.3

29.7

29.0

30.3

30.3

30.3

30.4

30.2

29.8

MgO

21.0

21.3

21.7

21.1

20.8

21.3

21.1

21.4

20.4

20.9

20.8

20.8

21.2

21.4

21.1

21.5

2.1.7

21.0

21.5

21.8

21.1

20.9

21.0

21.5

21. 0

17.4

21.0

21.5

20.9

21.3

21.4

21.5

21.5

21.5

2.1.3

TAHI.K 2. Chemical analyses (in percent) of dolomite samples SG-J/S 

[Analyst, Esther ClafTy]

No.

36

37

38

39

40

41

42

43

SiO2

1.59

1.35

1.70

9.93

7.33

.84

1.56

1.58

R2 03

0.36

.38

.41

1.08

.43

.31

.40

.26

CaC03

53.60

53.60

53.19

49.19

50.41

53.99

53. 58

53.60

MgCOa

44.36

44.07

44.70

39.80

41.83

44.80

44.40

44.50
134 CONTRIBUTIONS TO ECONOMIC GEOLOGY

1 to 35. The section Avas measured from the top of the cliffs (about 

120 feet above the flat on the north side of the hill), southward over 

the middle peak and across the southwest part of the quarry, down to 

the cliffs south of the quarry floor. Although the section is not continuous, it indicates the chemical composition and the lithologic characteristics of the dolomite along one traverse line across the widest 

part of the hill. The stratigraphic breaks caused by each fault are 

noted in the section.

Section of the Middle Cambri(m(?) dolomite deposit in Stevcns County, Wash.

Northport limestone of Weaver (1920) : Feet

14. Dolomite, light- and dark-gray. Contains black irregular masses 

strongly mottled with light-gray irregular dots and streaks. 

Forms lowest cliff ledge at southwest end of quarry face. Sample 35 of light-gray dolomite from near top of unit. Sample 34 

of black mottled dolomite from 13 ft above base of unit_____ 32

13. Dolomite, light-gray. Contains irregular black-gray masses. 

Veins and thin stringers of quartz constitute 1 to 5 percent of 

rock (estimate). Samples 32 and 33 from middle of unit_____ 16

12. Dolomite, as in unit 11, but slightly darker gray in upper part of 

the unit. Contains veins and irregular lenses of quartz. Sample 

31 from top of unit_________________..____________ 15

11. Dolomite, faint-blue to dull-light-gray, finely to medium crystalline, 

slightly vitreous on fresh fracture, imbedded or thick-bedded. 

Beds much shattered and contain thin quartz veins on joint faces. 

Sample 30 from 2 ft below top of unit. Sample 29 from 30 ft 

above base of unit. Sample 28 from 4 ft above base of unit__ 49

Unit 11 is broken by one of the younger normal faults. The 

thickness of duplicated beds is unknown.

10. Dolomite, pale- and light-gray, some beds dark gray, no black-gray 

masses or beds; finely crystalline, dense, hard, slightly vitreous 

on fresh fracture. Contains some quartz in 1 to 25 min veins 

which follow joints. Quartz more abundant in a 6-ft wide 

zone, 4 to 10 ft east of a dike intrusion. Sample 27 from 1 ft 

below top of unit. Sample 26 from 6 ft above base of unit. 

Sample 25 from base of unit__________ __________ IS

The section between units 9 and 10 is intruded by a dike and 

broken by one of the older normal faults. The throw probably 

was small, but the thickness of duplicated beds is unknown. 

9. Dolomite, light-gray, fine to microcrystalline, thick-bedded, dense. 

Some irregular masses of black dolomite. Sample 24 from top 

of unit____________________________________ 31 

8. Dolomite, as in units 5 to 7, but contains smaller and fewer black- 

. gray masses. Veins and stringers of siliceous dolomite and 

quartz still present. Sample 23 from 16 ft below top of unit. 

Sample 22 from 24 ft above base of unit. Sample 21 from 12 ft 

above base of unit-_ ___ _____________ 62 

7. Dolomite, as in unit 4, but contains more black beds. Sample 20

from top of unit. Sample 19 from 20 ft above base of unit___ 28
DOLOMITE DEPOSIT NEAR MARBLE, WASHINGTON 135

Section of the Middle Cambrian (?) dolomite deposit in Stevens County, 

Wash. Continued

Northport limestone of Weaver (1920) Continued Feet,

6. Dolomite, similar to unit 5. Sample 18 from 6 ft below top of unit. 

Sample 17 from 48 ft above base of unit. Sample 16 from 24 

ft above base of unit__________________ _____ TO

5. Dolomite, dull-gray, thick-bedded, medium-crystalline to sugary; 

alternating bands of black-gray dolomite mottled with small 

light-gray spots and streaks. Contains a few veins of r-herty 

dolomite and quartz. Sample 15 from 8 ft below top of unit. 

Sample 14 from 38 ft above base of unit. Sample 13 from 12 

ft above base of unit___________________ __ 64

4. Dolomite, dull-gray, gray, and blue-gray banded, finely to medium 

crystalline, thick-bedded or imbedded. Sample 12 from top 

of unit. Sample 11 from 23 ft below top of unit. Sample 10 

from 32 ft above base of unit______________ _____ 88

3. Dolomite, middle part of unit covered. Dolomite dull gray in lower 

part, faint blue gray in upper part. Sample 9 from top of unit. 

Sample 8 from 10 ft below top of unit. Sample 7 from 16 ft 

above base of \init____________________ __ 50

2. Dolomite, pale-gray, white-gray to faint-blue-gray, hard, finely 

to medium crystalline. Contains a little sericite along joint 

faces; also irregular veinlets of white quartz. Weathers pale 

gray. Sample 6 from top of unit. Sample 5 from 21 ft below 

top of unit. Sample 4 from 23 ft above base of unit_ ____ 59

1. Dolomite, thick-bedded, pale-gray, finely to medium crystalline, 

dense, hard. Some irregular beds of black-gray dolomite mottled 

light gray in spots or stringers 2 mm wide and 10 to 25 mm long. 

Some beds contain veins 1/25 to 8 in. thick of white glassy quart./ 

along joint faces. Sample 2 from 29 ft below top of unit 

Sample 1 from base of unit_______________ _____ 47

Total__________________________________ 629

SILICA AND OTHER IMPURITIES

Silica as quartz, the principal impurity in the dolomite, is so abundant and irregularly distributed that much of tl\e deposit may not 

be usable as a magnesium ore. (See pis. 14, 15.) Quartz occurs as 

(1) veinlets 0.5 to 5 mm thick (fig. 32), (2) irregularly walled and 

some smooth-walled veins as much as 15 inches thick (fig. 36), (3) 

sharp, angular ioslated fragments or nodules (fig. 35), (4) solid or 

vuggy cement around dolomite breccia fragments (fig. 37), and (5) 

vuggy masses (fig. 33). In addition, silica doubtless is present as 

microscopic quartz grains and in chemical combination as silicate 

minerals. Neither chert nor chalcedony was identified in the dolomite.

Silica is most conspicuous in white glassy quartz veins, most of 

which (see figs. 32, 34, 36) were deposited along joints. Much of the 

quartz in the breccias is stained tan buff and is slightly granular. The 

silica in the vuggy masses is dull gray and porous and superficially 

resembles siliceous sinter. The white quartz veins were deposited 

along intersecting sets of joints (fig. 32), and the quartz in the breccia
136 CONTRIBUTIONS TO ECONOMIC GEOLOGY

FIGURE 32. Continuous white quartz vein on intersecting joints.

FIGURE 33. Irregularly intersecting vuggy quartz veins in dark-gray dolomite.

zones is unbroken around the dolomite fragments, thus indicating 

that the silica was deposited after jointing and faulting. Quartz 

veins are common in the metamorphosed pre-Cambrian and Paleozoic 

rocks of northeastern Washington and probably are related in origin 

to the granites that intruded these rocks in Tertiary time.

The samples of crushed dolomite from the quarry have averaged 

more than 3 percent silica, which is probably representative of the
DOLOMITE DEPOSIT NEAR MARBLE, WASHINGTON 137

FIGURE 34. White quartz vein enclosing angular fragments of dolomite.

FIGURE 35. ;Angular nodules of white quartz in dull-gray dolomite.

3 .'"'entire deposit. However, the siliceous zones shown on the map may 

contain as much as 10 or 15 percent of SiO2 -

The other principal impurities in the dolomite are oxides of aluminum and iron. The relative amount of each is unknown as they are 

represented in the analyses as R2O3 . In many of the samples, however, 

the R2O3 is less than 0.8 percent, an amount that is not excessively objectionable in reducing dolomite with ferrosilicon. The aluminum
138 CONTRIBUTIONS TO ECONOMIC GEOLOGY

FIUUKK 30. Large vein of white quartz.

oxide probably represents original argillaceous material in the dolomite, but much of the iron oxide may have been introduced later.

ORIGIN OF THE DOLOMITE

Dolomite may be formed either during or closely following deposition of the original sediment in the sea, or later by alteration of 

original limestone by magmatic magnesium-bearing solutions.

Replacement dolomite characteristically contains unreplaced blocks 

and fragments of limestone, many open cavities, and irregular contacts. It is commonly coarse grained and exhibits considerable 

variation in grain size. These features have been described by Hewett 

(1931, p. 57-61; 1928, p. 821-863) and have been further treated by 

the writer in his report on the dolomite deposit at Sloan, Nev. (Deiss, 

1952, p. 13,2-134). The dolomite at Marble is a bedded deposit and
DOLOMITE DEPOSIT NEAR MARBLE, WASHINGTON 139

FKMIKE 37. Buff-colnroil iiimrtz surrounding leadicd fragments of dolomite

breccia.

contains none of the characteristics indicative of replacement origin. 

Therefore, it is thought that dolomiti/cation occurred at or shortly 

following the time of deposition of the original sediment. It should 

be pointed out that much of the Northport limestone, of which the 

dolomite near Marble is a part, is limestone. However, the relations 

of the two rocks were not exposed for observation in (lie field. Park 

and Cannon (1948, p. 45) observed that the location of bedded dolomite 

in the Metaline district nearby bears no direct relation to deformation structures, and they concluded that "regional dolomitization was 

probably accomplished before the introduction of the ore-bearing solutions, and it may have taken place early in the structural history." The 

same conclusion applies to the dolomite at Marble.

MINING CONDITIONS AND MKTHODS

The steep-sided dolomite hill and the surrounding nearly level flat 

(fig. 29) provide ideal conditions for economical mining and for operation of the crushing and screening plant and the railroad spur. The 

climate in the valley of the Columbia liiver is not so severe as might 

be expected near the 49th parallel at an altitude of 1,900 feet. Snow 

retards quarry operations during some winters but rarely causes a
140 CONTRIBUTIONS TO ECONOMIC GEOLOGY

complete stoppage of work. F. W. Sandoz (personal communication, 

November 19,1943) says: "Snow reduces production 10 percent in open 

winters and as much as 20 percent during severe winters."

QUARRY OPERATIONS

The dolomite is mined by benching the main quarry face. The 

. lower face is shot at the same rate as the benches in order that rock 

blasted on the benches will fall directly to the quarry floor. Boulders 

larger than 30 inches in diameter are broken by plug shots, and the rock 

is loaded into buggies by either a 3%- or a 3%-yard power shovel. 

One shovel at a time handles enough rock to supply the crushing plant, 

which has a rated capacity of 2,500 tons for 8 hours' operation. Except for the small amount shoved off the benches with bulldozers, all 

rock is moved on the quarry floor. The buggies dump the dolomite 

into a hopper, from which the dolomite moves on a steel conveyor to 

a "grizzly" and then to the primary crusher.

CRUSHING AND SCREENING

The dolomite is crushed in three gyratory crushers and screened 

to four sizes, referred to as grades 1,2, 3, and fines. The sizes in grade 

1 are minus 1%, plus 1 inch; in grade 2 are minus 1, plus % inch; in 

grade 3 are minus %, plus % inch; and fines are minus i/4 inch. The 

crushed rock is loaded by gravity from storage bins into open railroad 

cars on both sides of the storage building. The fines are loaded similarly into cars, buggies, and trucks from bins in the fines building. 

About 20 percent of the rock that enters the plant results in fines not 

used for ore.

PRODUCTION

The quarry and mill were put in operation April 16,1943. Until 

mid-November 1943, about 23,400 tons of dolomite a month was quarried and milled and 19,500 tons was shipped. The largest tonnage 

quarried in 8 hours "probably was 800" (F. W. Sandoz, personal communication, November 19, 1943). Failure to attain greater production was attributed to a shortage of railroad cars. The manpower 

shortage at the Spokane Works of the Electro Metallurgical Co. has 

held production to approximately 40 percent of the plant's rated 

capacity, which in turn necessitated reduced operations at the quarry. 

In mid-November 1943, production at the quarry was reduced to 8 cars 

per day, or a monthly average of 11,000 tons of ore plus 2,200 tons of 

fines, a total of 13,200 tons. The plant was closed on January 1,1945. 

In 1952 operations were resumed at the quarry and the Spokane magnesium plant, but no details concerning these recent operations are 

available.
DOLOMITE DEPOSIT NEAR MARBLE, WASHINGTON 141

SELECTED BIBLIOGRAPHY

Daly, R. A., 1912, Geology of the North American Cordillera at the forty-ninth 

parallel: Canada Geol. Survey Mem. 38, pt. 1, 573 p.

Deiss, C. F., 1952, Dolomite deposit near Sloan, Nev.: U. S. Geol. Survey Bull. 

973-C, p. 107-141.

Flint, R. F., 1936, Stratified drift and deglaciation of eastern Washington: Geol. 

Soc. America Bull., v. 47, p. 1849-1884.

Hewett, D. F., 1928, Dolornitization and ore deposition: Econ. Geology, v. 23, p. 

821-863.

 1931, Geology and ore deposits of the Goodsprings quadrangle, Nevada: 

U. S. Geol. Survey Prof. Paper 162, p. 57-61.

Landes, Henry, 1934, The mineral resources of the Columbia River basin in 

eastern Washington and parts of northern Idaho: U. S. 73d Gong., 1st sess., 

H. Doc 103, v. 2, p. 1068-1107.

Pardee, J. T., 1918, Geology and mineral deposits of the Colville Indian Reservation, Wash.: U. S. Geol. Survey Bull. 677, 186 p.

Park, C. F., Jr., 1938, Dolomite and jasperoid in the Metaline district, northeastern Washington : Econ. Geology, v. 33, p. 709-729.

Park, C. F., Jr., and Cannon, R. S., Jr., 1943, Geology and ore deposits of the 

Metaline quadrangle, Washington: U. S. Geol. Survey Prof. Paper 202, 81 p.

Weaver, C. E., 1920, The mineral resources of Stevens County: Wash. [State] 

Geol. Survey Bull. 20, 350 p.

O