Summary Narrative of an Exploratory Expedition to the Sources of the Mississippi River, in 1820 / Resumed and Completed, by the Discovery of its Origin in Itasca Lake, in 1832

by Henry Rowe Schoolcraft

VI.

Report on the Copper Mines of Lake Superior. By Henry R. Schoolcraft.

To the Hon. John C. Calhoun, Secretary of War.

Vernon (Oneida County, N. Y.), November 6, 1820.

Sir: I have now the honor to submit such observations as have occurred to me, during the recent expedition under GOV. Cass, in relation to the copper mines on Lake Superior; reserving, as the subject of a future communication, the facts I have collected on the mineralogy and geology of the country explored generally.

The first striking change in the mineral aspect of the country north of Lake Huron, is presented near the head of the Island of St. Joseph, in the River St. Mary, where the calcareous strata of secondary rocks are succeeded by a formation of red sandstone, which extends northward to the head of that river at Point Iroquois, producing the falls called the Sault de Ste. Marie, fifteen miles below; and thence stretching northwest, along the whole southern shore of Lake Superior, with the interruptions noted, to Fond du Lac.

This extensive stratum is perforated at various points by upheaved masses of sienitic granite and trap, which appear in elevated points on the margin of the lake at Dead River, Keweena Point, Presque Isle, and the Chegoimagon Mountains. It is overlaid, in other parts, by a stratum of gray or neutral-colored sandstone, of uncommon thickness, which appears in various promontories along the shore, and, at the distance of ninety miles from Point Iroquois, constitutes a lofty perpendicular and caverned wall, upon the water's edge, called the Pictured Rocks.

So obvious a change in the geological character of the rock strata, in passing from Lake Huron to Lake Superior, prepares the observer to expect a corresponding one in the imbedded minerals and other natural features—an expectation which is realized during the first eighty leagues, in the discovery of various minerals. The first appearances of copper are seen at Keweena Point, two hundred and seventy miles beyond the Sault de Ste. Marie, where the debris and pebbles along the shore of the lake contain native copper disseminated in particles varying in size from a grain of sand to a mass of two pounds' weight. Many of the detached stones of this Point are also colored green by the carbonate of copper, and the rock strata exhibit traces of the same ore. These indications continue to the River Ontonagon, which has long been noted for the large masses of native copper found upon its banks, and about the contiguous country.

This river is one of the largest of thirty tributaries, mostly small, which flow into the lake between Point Iroquois and Fond du Lac. It originates in a district of mountainous country intermediate between the Mississippi River and lakes Huron and Superior. After running in a northern direction for about one hundred and twenty miles, it enters the latter at the computed distance of fifty miles west of the portage of Keweena, in north latitude 46° 52´ 2´´, according to the observations of Capt. Douglass. It is connected, by portages, with the Monomonee River of Green Bay, and with the Chippewa River of the Mississippi. At its mouth there is a village of Chippewa Indians of sixteen families, who subsist chiefly on the fish taken in the river. Their location, independent of that circumstance, does not appear to unite the ordinary advantages of an Indian village of the region.

A strip of alluvial land of a sandy character extends from the lake up the river three or four leagues, where it is succeeded by hills of a broken, sterile aspect, covered, chiefly, with a growth of pine, hemlock, and spruce. Among these hills, which may be considered as lateral spurs of the Porcupine Mountains, the copper mines, so called, are situated, at the computed distance of thirty-two miles from the lake, and in the centre of a region characterized by its wild, rugged, and forbidding appearance. The large mass of native copper lies on the west bank of the river, at the water's edge, at the foot of an elevated bank, part of which appears to have slipped into the river, carrying with it the mass of copper, together with detached blocks of sienitic granite, trap-rock, and other species common to the soil at that place.

The copper, which is in a pure and malleable state, lies in connection with serpentine rock, one face of which it almost completely overlays. It is also disseminated in masses and grains throughout the substance of the rock. The surface of the metal, unlike most oxidable metals which have been long exposed to the atmosphere, presents a metallic brilliancy, which is probably attributable to the attrition of the semi-annual floods of the river.

The shape of the rock is very irregular; its greatest length is three feet eight inches; its greatest breadth, three feet four inches, with an average thickness of twelve inches. It may, altogether, contain eleven cubic feet.[ [207] It exceeds, in size, the great mass of native iron found some years ago on the banks of Red River, in Louisiana. I have computed the weight of metallic copper in the rock at twenty-two hundred pounds, which is about one-fifth of the lowest estimate made of it by former visitors. Henry, who visited it in 1766, estimated its weight at five tons. The quantity may, however, have been much diminished since its discovery, and the marks of chisels and axes upon it, with the discovery of broken tools, prove that portions have been cut off and carried away. Notwithstanding this reduction, it may still be considered one of the largest and most remarkable bodies of native copper on the globe, and is, so far as known, only exceeded in weight by a specimen found in a valley in Brazil, weighing twenty-six hundred and sixty-six Portuguese pounds. Viewed as a subject of scientific interest, it presents illustrative proofs of an important character. Its connection with a rock which is foreign to the immediate section of country where it lies,[ [208] indicates a removal from its original bed; while the intimate connection of the metal and matrix, and the complete envelopment of masses of the copper by the rock, point to a common and contemporaneous origin, whether that be referable to volcanic agency or water. This conclusion admits of an obvious application to the beds of serpentine and other magnesian rock found in other parts of the lake.

Several other large masses of native copper have been found, either on this river or within the basin of the lake, at various periods since the country has been known, and taken into different parts of the United States and of Europe. A recent analysis of one of these specimens, at the University of Leyden, proves it to be native copper in a state of uncommon purity, and uncombined with any notable portion of either gold or silver.

A mass of copper, weighing twenty-eight pounds, was discovered on an island in Lake Superior, eighty miles west of the Ontonagon. It was taken to Michilimackinac and disposed of. The War Department was formerly supplied with a specimen from this mass, and the analysis above alluded to is also understood to have been made from a portion of it. A piece weighing twelve pounds was found at Winnebago Lake. Other discoveries of this metal have been made, within the region, at various times and places.

The existence of copper in the region of Lake Superior appears to have been known to the earliest travellers and voyagers.

As early as 1689, the Baron La Hontan, in concluding a description of Lake Superior, adds: "That, upon it, we also find copper mines, the metal of which is so fine and plentiful that there is not a seventh part lost from the ore."—New Voyages to North America, London, 1703.

In 1721, Charlevoix passed through the lakes on his way to the Gulf of Mexico, and did not allow the mineralogy of the country to escape him.

"Large pieces of copper are found in some places on its banks [Lake Superior], and around some of the islands, which are still the objects of a superstitious worship among the Indians. They look upon them with veneration, as if they were the presents of those gods who dwell under the waters. They collect their smallest fragments, which they carefully preserve, without, however, making any use of them. They say that formerly a huge rock of this metal was to be seen elevated a considerable height above the surface of the water, and, as it has now disappeared, they pretend that the gods have carried it elsewhere; but there is great reason to believe that, in process of time, the waves of the lake have covered it entirely with sand and slime. And it is certain that in several places pretty large quantities of this metal have been discovered without being obliged to dig very deep. During the course of my first voyage to this country, I was acquainted with one of our order (Jesuits) who had been formerly a goldsmith, and who, while he was at the mission of Sault de Ste. Marie used to search for this metal, and made candlesticks, crosses, and censers of it, for this copper is often to be met with almost entirely pure."—Journal of a Voyage to North America.

In 1766, Captain Carver procured several pieces of native copper on the shores of Lake Superior, or on the Chippewa and St. Croix Rivers, which are noticed in his travels, without much precision, however, as to locality, &c. He did not visit the southern shores of Lake Superior, east of the entrance of the Brulé, or Goddard's River, but states that virgin copper is found on the Ontonagon. Of the north and northeastern shores, he remarks: "That he observed that many of the small islands were covered with copper ore, which appeared like beds of copperas, of which many tons lay in a small space."—Three Years' Travels, &c.

In 1771 (four years before the breaking out of the American Revolution), a considerable body of native copper was dug out of the alluvial earth on the banks of the Ontonagon River by two adventurers, of the names of Henry and Bostwick, and, together with a lump of silver ore of eight pounds' weight, it was transported to Montreal, and from thence shipped to England, where the silver ore was deposited in the British Museum, after an analysis had been made of a portion of it, by which it was determined to contain 60 per cent. of silver.

These individuals were members of a company which had been formed in England for the purpose of working the copper mines of Lake Superior. The Duke of Gloucester, Sir William Johnson, and other gentlemen of rank were members of this company. They built a vessel at Point aux Pins, six miles above the Sault Ste. Marie, to facilitate their operations on the lake. A considerable sum of money was expended in explorations and digging. Isle Maripeau and the Ontonagon were the principal scenes of their search. They found silver, in a detached form, at Point Iroquois, fifteen miles above the present site of Fort Brady.

"Hence," observes Henry, "we coasted westward, but found nothing till we reached the Ontonagon, where, besides the detached masses of copper formerly mentioned, we saw much of the same metal imbedded in stone.

"Proposing to ourselves to make a trial on the hill, till we were better able to go to work upon the solid rock, we built a house, and sent to the Sault de Ste. Marie for provisions. At the spot pitched upon for the commencement of our operations, a green-colored water, which tinges iron of a copper color, issued from the hill, and this the miners called a leader. In digging, they found frequent masses of copper, some of which were of three pounds' weight. Having arranged everything for the accommodation of the miners during the winter, we returned to the Sault.

"Early in the spring of 1772, we sent a boat-load of provisions, but it came back on the 20th day of June, bringing with it, to our surprise, the whole establishment of miners. They reported that, in the course of the winter, they had penetrated forty feet into the face of the hill, but, on the arrival of the thaw, the clay, on which, on account of its stiffness, they had relied, and neglected to secure it by supporters, had fallen in. That, from the detached masses of metal which, to the last, had daily presented themselves, they supposed there might be ultimately reached a body of the same, but could form no conjecture of its distance, except that it was probably so far off as not to be pursued without sinking an air shaft. And, lastly, that the work would require the hands of more men than could be fed in the actual situation of the country.

"Here our operations, in this quarter, ended. The metal was probably within our reach, but, if we had found it, the expense of carrying it to Montreal must have exceeded its marketable value. It was never for the exportation of copper that our company was formed, but always with a view to the silver, which it was hoped the ores, whether of copper or lead, might in sufficient quantity contain."—Travels and Adventures of Alexander Henry.

[In the summer of 1832, being detained by head winds at the mouth of Miner's River, on Lake Superior, I observed the names of several persons engraved on the sand rock, but much obliterated by the water's dashing over the rock. Tradition represents that Henry's miners were detained there, and that they made explorations of the river, which is named from the circumstance. The stream is a mere brook, coming over the shelving sand rock, which is a part of the precipitous range of the Pictured Rocks.]

Sir A. Mackenzie passed through Lake Superior, on his first voyage of discovery, in 1789. He remarks: "At the River Tennagon (Ontonagon) is found a quantity of virgin copper. The Americans, soon after they got possession of the country, sent an agent thither; and I should not be surprised to hear of their employing people to work the mine. Indeed, it might be well worthy the attention of the British subjects to work the mines on the north coast, though they are not supposed to be so rich as those on the south."—Voyages from Montreal through the Continent of North America.

It is difficult to conceive what, however, is apparent, from the references of Dr. Franklin to the subject, that the supposed mineral riches of Lake Superior had an important bearing on the discussions for settling the ultimate northern boundary of the United States. The British ambassadors had, it seems, from an old map which is before me, claimed a line through the Straits of Michilimackinac and the Illinois and Mississippi rivers, to the Gulf of Mexico.

The attention of the United States Government appears first to have been turned toward the subject during the administration of President John Adams, when the sudden augmentation of the navy rendered the employment of copper in the equipment of ships an object of moment. A mission was therefore authorized to proceed to Lake Superior, of the success of which, as it has not been communicated to the public, nothing can, with certainty, be stated; but from inquiries which have been made during the recent expedition, it is rendered probable that the actual state of our Indian relations, at the time, arrested the advance of the officer into the region where the most valuable beds of copper were supposed to exist, and that the specimens transmitted to Government were procured through the instrumentality of some friendly Indians, employed for the purpose.

Such are the lights which those who have preceded me in this inquiry have thrown upon the subject, all of which have operated in producing public belief in the existence of extensive copper mines on Lake Superior. Travellers have generally coincided that the southern shore of the lake is most metalliferous, and that the Ontonagon River may be considered as the seat of the principal mines. Mr. Gallatin, in his report on the state of American manufactures in 1810, countenances the prevalent opinion, while it has been reiterated in some of our literary journals, and in the numerous ephemeral publications of the times, until public expectation has been considerably raised in regard to them.

Under these circumstances, the recent expedition under Gov. Cass entered the mouth of the Ontonagon River on the 27th of June, having coasted along the southern shore of the lake from the head of the River St. Mary. We spent four days upon the banks of that stream, in the examination of its mineralogy, during which the principal part of our party was encamped at the mouth of the river. Gov. Cass, accompanied by such persons as were necessary in the exploration, proceeded, in two light canoes, to the large mass of copper which has already been described. We found the river broad, deep, and gentle for a distance, and serpentine in its course; then becoming narrower, with an increased velocity of current, and, before reaching the Copper Rock, full of rapids and difficult of ascent. We left our canoes at a point on the rapids, and proceeded on foot, across a rugged tract of country, around which the river formed an extensive semicircle. We came to the river again at the locality of copper. In the course of this curve the river is separated into two branches of nearly equal size. The copper lies on the right-hand fork, and it is subsequently ascertained that this branch is intercepted by three cataracts, at which the river descends over precipitous cliffs of sandstone. The aggregate fall of water at these cataracts has been estimated at seventy feet.

The channel of the river at the Copper Rock is rapid and shallow, and filled with detached masses of rock, which project above the water. The bed of the river is upon sandstone, similar to that under the Palisades on the Hudson. The waters are reddish, a color which they evidently owe to beds of ferruginous clay. The Copper Rock lies partly in the water. Other details in the geological structure and appearance of the country are interesting; but they do not appear to demand a more particular consideration in this report.

During our continuance upon this stream, we procured from an Indian a separate mass of copper weighing nearly nine pounds; which will be forwarded to the War Department. This specimen is partially enveloped with a crust of green carbonate of copper. Small fragments of quartz and sand adhere to the under side, upon which it would appear to have fallen in a liquid state. Several smaller pieces of this metal were procured during our excursion up the Ontonagon, or along the shores of the lake east of this stream.

It may be added that discoveries of masses of native copper, like those of gold and other metals, are generally considered indicative of the existence of mines in the neighborhood. The practical miner regards them as signs which point to larger bodies of the same metals, in the earth, and he is often determined by discoveries of this nature in the choice of the spot for commencing his labors. The predictions drawn from such evidence are more sanguine in proportion to the extent of the discovery. They are not, however, unerring indications, and appear liable to many exceptions. Metallic masses are sometimes found at great distances from their original repositories; and the latter, on the contrary, sometimes occur in the earth, or imbedded in rock strata, where there have been no great external discoveries.

From all the facts, which I have been able to collect on Lake Superior, and after a full deliberation upon them since my return, I have drawn the following conclusions:—

1. That the diluvial soil along the banks of the Ontonagon River, extending to its source, and embracing the contiguous region, which gives origin to the Monomonee River of Green Bay, and to the Wisconsin, Chippewa, and St. Croix Rivers of the Mississippi, contains very frequent, and several extraordinary masses of native, or metallic copper. But that no body of this metal, which is sufficiently extensive to become the object of profitable mining operations, has yet been found at any particular place. This conclusion is supported by the facts adduced, and, so far as theoretical aids can be relied upon, by an application of those facts to the theories of mining. A further extent of country might have been embraced, along the shores of Lake Superior, but the same remark appears applicable to it.

2. That a more intimate knowledge of the mineralogical resources of the country, may be expected to result in the discovery of valuable ores of copper, in the working of which occasional masses and veins of the native metal, may materially enhance the advantages of mining. This inference is rendered probable by the actual state of discoveries, and by the geological character of the country.

These deductions embrace all I have to submit on the mineral geography of the country, so far as regards the copper mines. Other considerations arise from the facilities which the country may present for mining—its adaptation to the purposes of agriculture—the state and disposition of the Indian tribes, and other topics which a design to commence metallurgical operations would suggest. But I have not considered it incumbent upon me to enter into details upon these subjects. It may, in brief, be remarked that the remote situation of the country does not favor the pursuit of mining. It would require the employment of a military force to protect such operations. For, whatever may be their professions, the Indian tribes of the north possess strong natural jealousies, and in situations so remote, are only to be restrained from an indulgence in malignant passions, by the fear of military chastisement.

In looking upon the southern shore of Lake Superior, the period appears distant, when the advantages flowing from a military post upon that frontier, will be produced by the ordinary progress of our settlements—for it presents but few enticements for the agriculturalist. A considerable portion of the shore is rocky, and its alluvions are, in general, of too sandy and light a character for profitable husbandry. With an elevation of six hundred and forty-one feet above the Atlantic, and drawing its waters from territories situated north of the forty-sixth degree of north latitude, Lake Superior cannot be represented as enjoying a climate favorable to the productions of the vegetable kingdom. Its forest trees are chiefly those of the fir kind, mixed with varieties of the betula, lynn, oak, and maple. Meteorological observations indicate, however, a warm summer, the average observed heat of the month of June being 69. But the climate is subject to a long and severe winter, and to sudden transitions of the summer temperature. We saw no Indian corn among the natives.

A country lacking a fertile soil, may still become a rich mining country, like the county of Cornwall in England, the Hartz Mountains in Germany, and a portion of Missouri, in our own country. But this deficiency must be compensated by the advantages of geographical position, a contiguous or redundant population, partial districts of good land, or a good market. To these, the mineral districts of Lake Superior can advance but a feeble claim, while it lies upwards of three hundred miles beyond the utmost point of our settlements, and in the occupation of savage tribes whose hostility has been so recently manifested.

Concerning the variety, importance, and extent of its latent mineral resources, I think little doubt can remain. Every fact which has been noticed tends to strengthen the belief that future observations will indicate extensive mines upon its shores, and render it an attractive field of mineralogical discovery. In the event of mining operations, the facilities of a ready transportation of the crude ores to the Sault de Ste. Marie, will point out that place as uniting, with a commanding geographical position, superior advantages for the reduction of the ores, and the general facilities of commerce. At this place, a fall of twenty-two feet, in the river, in the distance of half a mile, creates sufficient power to drive hydraulic works to any extent; while the surrounding country is such as to admit of an agricultural settlement.

I accompany this report with a geological sketch of a vertical section of the left bank of the Mississippi at St. Peter's, embracing a formation of native copper. This formation was first noticed by the officers of the garrison, who directed the quarrying of stone at this spot. The masses of copper found are small, none exceeding a pound in weight.

I have the honor to be, sir,
Very respectfully,
Your obedient servant,
HENRY R. SCHOOLCRAFT.