STONE.

Very little systematic quarrying has as yet been done in the state. The Stafford quarry, one mile from Velva, has furnished stone for a handsome and substantial building in that town. A sandstone which outcrops along the Missouri river has been utilized for foundations in Washburn. In Emmons county somesandstone has been used for building, especially at Linton. Small quantities of sandstone have been used at Dickinson.

Large sandstone quarries are practical, and a number of suitable locations only await a sufficient demand to justify extensive development.

The granite and gneiss boulders in the glaciated area are more important at present from an economic standpoint than are the native sandstones. Throughout the eastern half of the state, except in the Red river valley where surface boulders are scarce, they are used extensively for foundations and sometimes large buildings are constructed of them. They may be dressed easily and present a handsome appearance. The foundations of the buildings of the asylum for the insane at Jamestown show how effectively they may be used. Their cost varies with local conditions, but for many localities they should be considered as a possibility before brick for foundations. At Jamestown, under the contract for the erection of the asylum buildings, the boulders were gathered, aauled, dressed to eleven-inch courses with sunk joints, and laid in the wall for $10 a cord.

GRAVEL.

It is impossible to estimate the value of the great gravel deposits of North Dakota, from which thousands of cars are taken annually for railroad ballast. They are conveniently distributed throughout the state and with increase of population will justify careful study, for they will furnish the most available road material. The deposits at Jamestown, which are seen by every traveler from the car window, are but samples of dozens of others, some of which are already opened by the railroads.

POTTERY GOODS.

As yet the valuable pottery clays of North Dakota are wholly undeveloped. They are destined, however, to figure conspicuously in the mineral statistics of the state.

THE LIGNITE COAL FIELDS

OF

NORTH DAKOTA

EXTENT OF THE LIGNITE AREA

While thin seams of lignite have been recognized in the eastern part of the state and have been described* at the southern bend of the Cheyenne river, in Township 135, Range 54, Section 32, which lies about twenty-five miles southwest of Valley City, and at other points nearly as far east, workable seams are not found, except in the Turtle mountains, till the center of the state is reached. The plateau known as Turtle mountains is an outlier of the lignite area proper, which may be roughly bounded on the east by a line beginning at the northern boundary of the state and thirty miles east of the Minneapolis, St. Paul & Sault Ste. Marie R. R., and extending southeast to Harvey, thence south through Steele to the southern boundary. More minute study, aided by well borings which will doubtless be made as the country is settled, will probably shift this line east or west at certain points, thirty or forty miles. The state lines are its boundaries on the north, west, and south, while outside of the state the lignite continues in these three directions. Only this region, in which workable seams of lignite may reasonably be looked for, is included in this report under the term, lignite area. Even when so restricted it is of very great extent, equal to at least half of the state of Ohio.

It is highly probable that lignite does not exist in seams of workable thickness in every part of this region, but it is equally probable that the fraction of the area lacking lignite in seams three or more feet thick is a small one, not more than one-fifth

* Upham in Monograph XXV, page 92, United States Geological Survey. Geol.-3

of the whole. These seams may not all be available, either on account of depth, or some other difficulty in mining and throughout a considerable part of the region are so thoroughly concealed by glacial drift that, without a knowledge of the underlying formations and of the surrounding country, their existence would be unsuspected.

TOPOGRAPHY OF THE LIGNITE AREA

The surface of the lignite area presents considerable variety. Areas that would be regarded as topographic types could readily be chosen from the moraines of Coteau du Missouri; from the older drift west of the moraine; from the Missouri valley; from the driftless area about Dickinson, and from the Bad lands.

THE WISCONSIN DRIFT PLAIN.

The extreme eastern portion of the lignite area lies within the coparatively leveml plain of the Wisconsin drift, the deposit formed by the last great ice invasion. Like this plain throug out the eastern part of the state, it is moderately rolling, and rarely presents the extremely level surface that characterizes it in Iowa. and Illinois. The interesting valleys of the Mouse and des Lacs rivers, which lie within this area, will be briefly described by Mr. Wood in his report on Ward county.

Rising rather sharply from the Wisconsin drift plain is the Coteau du Missouri, along the edge of which the lignite outcrops at a number of points which will be described in the subsequent text. The Coteau was studied along the Great Northern and Northern Pacific railroads, in a trip across country from Velva to Coal Harbor, and in a number of excursions back from the "Soo" road, and at all of these points its characteristics were quite constant. The rather sharp risc of its eastern face may be illustrated by the elevations of stations on the Great Northern. Des Lacs, 1902 feet above the sea, is on the prairie level, three hundred and fifty feet above Minot, which lies in the valley of the Mouse river. Berthold, twelve miles farther west, has an elevation of 2,087 feet. Wallace, six miles farther, is 2,187 feet high. From Wallace to Delta, a distance of five miles, an ascent of of seventy-six feet reaches the crest of the Coteau. From this point the descent of the railroad is gradual to the west, crossing the outer or Altamont moraine of the Wisconsin drift, and reaching the level of the lower terrace of the Missouri river at Williston. The upland level, however, rises gradually toward the west.