« AnteriorContinuar »
Upon the whole, a review of the resources and capabilities of this lead region, taken in connexion with its statistics, (in so far as it was possible to collect these,) induces me to say, with confidence, that ten thousand miners. could find profitable employment within its confines.
If we suppose each of these to raise daily one hundred and fifty pounds of ore, during six months only of each year, they would produce annually upwards of one hundred and fifty million pounds of lead ; more than is now furnished by the entire mines of Europe, those of Great Britain included.
This estimate, founded (as those who have perused the foregoing pages will hardly deny) upon reasonable data, presents, in a striking point of view, the intrinsic value and commercial importance of the country upon which I am reporting; emphatically, THE LEAD REGION OF NORTHERN AMERICA.
It is, so far as my reading and experience extend, decidedly the richest in the known world.
The copper ore of the Wiskonsin Territory forms an item in its mineral wealth, which would be considered of great importance, and would attract much attention, but for the superior richness and value of the lead, the great staple of the Territory.
This ore occupies, in the district under examination, the same geological position as the lead ore. It originates in the fissures of the cliff limestone. It has been spoken of, very incorrectly, as “float mineral ;" as if, like the fragments of native copper sometimes found in the diluvium of Western America, it had been conveyed to its present situation from a distance. This our examinations have disproved. Discoveries of copper ore have indeed been made on a sloping hill-side near Mineral Point, within three or four feet of the surface; and there the ore was found disseminated and imbedded in an och reous earth.* But on following this deposite to the oppo. site side of the ravine, (on section twenty.two, township five, range three east of the fourth principal meridian,) the copper ore was traced into a crevice, and a regular vein has there been worked to the depth of thirty or forly feet. The pieces of copper ore raised on this spot commonly weighed from a few ounces to ten or twelve pounds; and one mass thence procured was estimated at five hundred pounds.
The course of this copper vein is from southeast to northwest ; and if this line be produced, either way, from the discoveries at Mineral Point, it will strike, almost exactly, the discoveries of copper ore northwest on Blue river, and southeast on the Peccatonnica-a proof that the copper ore is not a superficial and vagrant deposite, but exists in veins of uniform bearing; and that these veins are continuous, and in all probability extensive.
It is found in several localities in sufficient abundance to repay well the labor of the miner. If there were a steady demand for copper ore in the Territory, the miners could afford, as I was informed by themselves, to raise copper ore at the same price as lead ore, namely, from one and a half to two cents per pound. It would be in good demand, and be extensively raised, but for the capital and skill necessary to reduce it; which are both
*This earth frequently contains particles, more or less numerous, of copper ore, and is then popularly termed gozzin," and employed as a flux in the copper furnaces. The gozzin of Wiskonsin yields, by analysis, from 6 to 9 per cent. of pure copper-a large percentage for such ore.
far greater than the lead-smelter requires; and, also, but for the scarcity of fuel. The copper ore of this region compares very favorably with the Cornwall copper ores. An analysis of a selected specimen of the best working Cornwall ore, and of three average specimens of Wiskonsin ore, showed that the latter contains from a fifteenth to a third more of copper than the former.
The Wiskonsin ore is of a very uniform quality. There was shipped from Ansley's ground, within a mile of Mineral Point, in the year 1838, 10 England, fifty thousand pounds of ore; which yielded (according to the statement of one of the gentlemen who shipped it) over twenty per cent. of pure copper. The average produce in the copper.mines of Cornwall may be stated at eight per cent.
There have been raised, at the Mineral Point mines, upward of a million and a half pounds of copper. At Ansley's copper furnace, one hundred and thirty-five thousand pounds of this was smelted; which yielded, in a very imperfect smelting furnace,” twelve thousand pounds pure copper, or about nine per cent. Mr. Ansley stated that he had not been able to procure a smelter acquainted with the mode of reducing copper ore; and it is impossible to say what the percentage might have been, had the reduction been conducted with skill, and in a well-constructed furnace.
The Wiskonsin copper-veins may rank among the most important that have yet been discovered in the mountain limestone formation. European copper-mines in that geological group (as in Staffordshire, Eugland,) usu
* Comparative analysis of three AVERAGE specimens of the solid copper ore from Wiskonsin, and
one specimen from Cornwall of what is there considered the best quality of copper ore.
Specific gravity of Wiskonsin ore from 3.692 to 3.866.
* Do. do. Cornwall " 3.564 to 3.595.
If we consider the earthy residuums as accidental, it appears from these analyses that the Cornwall ore is a compound of sulphuret of copper (probably a di-sulphuret of copper) and sulphuret of iron; and that the Wiskonsin ore is essentially a hydrous di-carbonate of copper, (the malachite of mineralogists,) composed of one alom carbonic acid, iwo atoms oxide of copper, and one atom of water, with a variable admixture of the oxides of iron, and little sulphuret of iron. In the third specimen there appears to be but little admixture of oxide of iron, ihat being replaced by a small percentage of sulphuret of copper.
ally yield very sparingly. Cornwall, which is the greatest copper country in the world, is composed entirely of crystalline, and the lower stratified rocks, chiefly slate, associated with granite and porphyry. The celebrated Pary's copper.mine, in the island of Anglesea, occurs in a mountain com. posed of primary slate.
This may seem an argument against the probable productiveness of the Wiskonsin copper-mines. Yet the formations in this western hemisphere are on a scale so extensive, compared with those in most parts of Europe, (witness a single coal-field equalling Great Britain in area,) that such an argument must be received with many qualifications. In addition to this, the indications in Wiskonsin, as far as they have been observed, and the analysis of the ore, afford strong presumptive evidence that capital and skill alone are required to render copper-mining in this district, at least for some time to come, an advantageous and profitable adventure.
One of the difficulties which here occurs in reducing the ore, namely, the lack of fuel, is common to the richest copper countries in Europe. The Cornwall copper ore is conveyed partly to Swansea and other portions of Wales, and partly to Liverpool, to be smelted in a coal region; and the same vessels which thus convey the less bulky material to the more bulky, (the ore to the fuel,) return laden with coal to supply the numerous and powerful steam-engines required, for draining and other purposes, at the Cornwall mines. And thus, in Wiskonsin, if copper ore be raised in quantities, it may be necessary to convey it south to the margin of the great Illinois coal-field—say to the mouth of Rock river. This would require a landcarriage of from ten to thirty miles, and a water-carriage of about one hundred. The Cornwall ore is transported to a greater distance than this.
It may be added, as an additional fact whereby to estimate the value of the Wiskonsin copper ore, that, in some of the European copper-mines, "the ore does not contain above three per cent. of pure copper, and yet it pays for working." Also, that in some of the Cornwall mines, the ore is worked profitably at a depth of more than two thousand feet “from the grass,” as the phrase there is.
Finally, the Wiskonsin copper ore derives additional value in consequence of being found in the vicinity of, and often in the same mine as, productive veins of
This ore, found both in Iowa and Wiskonsin, usually occurs in the fis. sures, along with the lead. It is chiefly the electric calamine-the carbonate of zinc of the mineralogist. Though a solid ore, it has an ochreous, earthy aspect, often resembling the cellular substance of bone: hence it is familiarly known among the miners by the name of “dry bones."
Notwithstanding its intrinsic value, which will before very long be duly appreciated, it is at present an object of especial aversion to the miner of Iowa and Wiskonsin. It frequently happens, in both Territories, that the lead ore in a fissure gradually diminishes, and eventually is entirely replaced by this zinc ore; or, as the disappointed workman, sometimes with a hearty curse, not very scientifically expresses it, “the dry bone eats out the mineral.”
At some of the diggings, large quantities of this carbonate of zinc can be procured. Thousands of tons are now lying in various locations on
the surface, rejected as a worthless drug-indeed, as a nuisance. It is known but to a few of the miners as a zinc ore at all. An analysis of this ore proves it to be a true carbonate of zinc, containing forty-five per cent. of the pure metal.
Sulphuret of zinc, (sometimes called blende, and, by the English miner, "black.jack,") is also abundant in the Wiskonsin mines. It contains from fifty-five to sixty-five per cent. of zinc, but is more difficult of reduction than the calamine.
Sheet zinc is becoming an article of considerable demand in the market. for culinary purposes, and as a covering for valuable buildings, instead of lead. But the chief consumption of this metal is in making brass, well known to be a compound of copper and zinc. In this process, the carbo. nate of zinc, previously calcined, is mixed with charcoal and granulated copper, and then exposed to a suitable heat. The common brass imported fiom England contains upwards of thirteen per cent. of zinc ; that of Paris, a little less; and the fine brass of Geneva, used in the nicer parts of watchmaking, contains as much as twenty-five per cent. of zinc.
Large quantities both of copper and zinc are now imported from Furope into the United States, to supply the continually increasing demand for brass. It is not improbable that the district now under consideration might furnish of both metals a sufficient amount, at least for many years to come, to supply the entire United States with brass of home produce and manu. facture.
Of zinc, at least, there is assuredly a sufficient supply, not only for that purpose, but also for exportation. All the zinc now produced in Great Britain is trifling in quantity, and quite insufficient for the demand ; so that a large quantity is imported annually into that island, chiefly from Ger. many and Belgium. The importation of zinc into England, in the year 1833, exceeded six millions and a half of pounds—a fact which may gire us an idea of the importance of this metal as an article of commerce.
Among the productive mineral resources of Iowa and Wiskonsin, the at present despised zinc ore may claim no contemptible rank.
The iron ore of this district is of excellent quality, and in unlimited abundance. I explored, a few years since, in company with Professor 'Troost, geologist of Tennessee, the iron-mines of that State, which already furnish iron to a considerable portion of the western States. And though I have seen no proof that iron exists in Iowa and Wiskonsin, in deposites
* Resulting thus:
Carbonic acid -
1.00 5.00 5.00 1.00 .30
100.00 Or, if the iron, alumina, and silex be regarded as accidental mixtures, the ore is an anhydrous carbonate of zinc, composed of one atom of carbonic acid, and one atom of oxide of zinc ; or, as it is sometimes called, electric calamine. It contains upwards of forty-five per cent. of metallic zinc. Ils specific gravity is from 3.77 to 3.89.
as extensive as in Tennessee, yet the locations of iron ore are as numerous, and the quality of the ore, in general, is as good.
In some of the townships, especially in the “Missouri limestone," on the Wiskonsin river, iron ore was found scattered in innumerable fragments over the entire surface, and of a quality so rich as to be crystallized in much perfection. Near the Mekoqueta, my sub-agents reported the discovery of large masses of iron ore, occurring over a very considerable district of country. The reports and specimens from that portion of the district induce me to believe that there iron ore can be found, on the surface alone, sufficient to supply several iron-furnaces for years to come.
Some of the specimens from these localities are the richest and most beautiful variety of pipe-ore I have ever seen, exhibiting a miniature resemblance to the basaltic columns of Staffa, or the Giant's Causeway.
Much of it is the hematite, the purest and most productive form of the hydrated brown oxide. *
In many of these locations, where iron ore is found in abundance, fuel, water-power, and the limestone for flux, are at hand. In the northern portion of the district, however, the scarcity of fuel presents a serious obstacle to the establishment of productive iron-works.
In Dr. Locke's report, under the head “magnetical node,” will be found an interesting account of a remarkable magnetical phenomenon, which seems to indicate the presence of some enormous mass of iron, or (if the expression be allowed) some “subterraneous iron-mountain, which may resemble, except in position, that of Missouri. The locality indicated is on the Wapsipinecon; and the axis of this node, as Dr. Locke's chart shows, is near the line dividing townships eighty-two and eighty-three, and about six miles west of the fifth principal meridian. .
The utility of magnetical observations on the dip and intensity of the needle, as an indication of the presence of protoxide of iron, and perhaps, also, of great masses of the brown oxide, is indisputable; and I consider myself fortunate in having been able to add to the other materials whereby to decide the value of the various locations of mineral lands in this district, the delicate and varied experiments of Dr. Locke.
The variation-chart appended to that gentleman's report shows a striking difference in the variation of the needle within a very short distance; and the greatest variation corresponds, in a remarkable manner, with the best locations of iron ore of which actual discoveries were made. If from this we may conclude that the variation is increased by the presence of large masses of ore, the above chart would usefully guide a further examination after the localities of iron ore in the district. It must, however, be remembered, that it is the protoxide which chiefly acts upon the needle, and that the same phenomenon may possibly be caused by comparatively small veins of that variety, as by a large mass of the brown oxide.
The richness of the iron-veins in this district cannot be correctly known until mines shall actually be opened ; which has not yet been done in any part of it. But more encouraging or more numerous surface-indications of an abundant supply of this useful metal can hardly offer themselves to the notice of the geologist. In a country more thickly settled, and with skill and capital to spare, these would speedily cause and justify the employment of whole villages of workmen.
* These ores of iron yield from 40 to 60 per cent. of the metal.