Box 17, Folder 3: Lead Mines 1865-1874

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[map of Illinous [Illinois] removed] Illinois

Report on the Geology of the Council Hill Lead Mines. By I. A. Lapham of Milwaukee Wis. [March 1865]

Having visited and examined the Lead Mines at Council Hill, and having studied the rock=formations found there, I now make the following report, embracing the facts observed, and conclusions properly deducible from the same. These mines are situated on sections twenty four and twenty five of the United States Government Land survey, two miles north= = west from Council Hill Station on the Illinois Central Rail Road, seven miles from Galena, and one hundred + sixty three miles west from Chicago. Their position may be more clearly seen by reference to the accompanying map. They are within what is known as the Upper Mississippi Lead District which occupies covers an area of about three thousand square miles, in the states of Illinois, Wisconsin and Iowa. This region has been scientifically examined by several distinguished geologists who have made known by their reports, its general characteristics character and value. Lead ore ^(galena) was been known to exist here as Early as the year 1700 ; and lead has been produced in greater or less quantity for nearly Eighty years ; the annual product at one time amounted to ^over fifty millions of pounds.

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The ore is found chiefly in veins, (or in loose material resulting from their disintegration) in the limestones of the Lower Silurian system of rocks. The veins are chiefly mostly in a yellowish Magnesian limestone which has from this circumstance been named the Galena [lead= bearing] limestone. It is Easily recognized by the fossils it contains, and by the peculiar features configuration of the country under which it lies. The Galena limestone It has its greatest development in the region about Council Hill, where it attains the thickness of about two hundred + fifty feet; from which it thinning out in every direction. It also presents here its ^usual characteristics in the greatest degree of perfection.

The veins which usually generally have a north=&= south or East= and= west direction, but are here found in both, crossing each other at right angles. They are of the kind known as "Gash veins," having been formed ^as is supposed by the shrinkage of the rock after during some Epoch of moderate heat, and not by those more general ^& deep seated movements which have produced the "true veins." While Gash veins are confined to the particular formations in which they are found, true veins cut the several rocks, down to an unknown depth. The veins of these Lead region under consideration do not extend reach below the base of the blue limestones, in which they are found.

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Below this Galena Limestone the ^so called "Blue Limestone" is found, having a thickness in many places of about fifty feet, including the gray fossiliferous layers in the middle, and the buff colored rock below. The lead= bearing veins extend down, in many cases to the bottom of this. Blue limestone. At the Geer mine a mile north west from the Council Hill mines, some of the shafts have been sunk through the Galena and into the upper portion of the Blue Limestone: and at the mouth of a small stream half a mile further west the Blue limestone is exposed to view.

Below The Blue Limestone ^rests upon a sandstone throughout rests upon a sardstne [sandstone] is found in the Lead region, (though not seen here) in which there are no Lead = veins.

The relative position and thickness of these several formations. will be more fully understood by reference ti [to] the accompanyng [accompanying] profile geological profile, which Extends from the Galena river on section twenty three, through the Council Hill mines and thence by the Station to the high lands a mile and a half south.

It will be observed that The Council Hill mines are ^now worked ^only in the upper portion of the Galena Limestone ; from which though

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^circumstance it may with reasonably be supposed that the veins and openings containing the ore may be traced to a considerable depth below the bottom of the present shafts; probably possibly to the bottom of the Blue limestone. The fact that The ^Several mines in the vicinity being are in the lower part of the Galena ^limestone, and extending even into the Blue, adds probability to this conjecture., The whole depth [v?] in which veins may be looked for at this place is about two hundred and fifty feet.

It is thus shown that the Council Hill Mines possess the characteristics (they and occupy the same geological position) which are usual in this remarkable lead= producing they occupy the same geol. position ; And give abundant promisse [promise] of future continud [continued] [productiveuns?] region ^'^ and hence I can see no reason why they should not continue to yield a quantity of ore sufficient to justify an the outlay of the capital required for their full development

The explorations that will be possible when the adit now being constructed shall be completed on the completion of the adit now being constructed, will determine all questions as to the depth to which it would be profitable to work these mines; and also whether more thorough drainage will be desirable.

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Such additional drainage may be effected by making an adit from the East Fork of Galena river a little below the rail road station, a distance of a mile and a half, by means of which the mines may be drained, without further expense to the depth of about one hundred and fifty feet below the bottom of the present adit. The map will show that this proposed adit will drain other productive mines ; and it is quite probable that new veins and lead bearing crivaces [crevaces] openings may be revealed; possibly sufficient to defray all its cost.

The lead ore found in these mines is almost a pure sulphuret of lead (galena) containing 86.6 per cent. of metallic lead and 13.4 per cent. of Sulphur; There is with scarcely a trace of silver. Its purity is further indicated by the absence of barytes, and the ores of zinc; and by the scarcity of iron pyrites. The ore ^usually fills the whole breadth thickness of the veins, without gangue or vein = stone.