| East Dubuque Local Area History Project | |
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 There are pockets of lead in the layers of the hills |
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Millions of years ago, the earth was just a big ball of liquid rock. As it cooled, it formed layers of rock. There are many layers of rock in the earth. Our earth is made up of four zones: the crust, the mantle, the inner core, and the outer core. The crust is the thinnest layer of all. It is 10-25 miles thick. The deepest mines are only 3 miles deep. |
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| The crust of the earth is made of tectonic plates that move and shift. When the tectonic plates shift, they cause earthquakes and volcanoes. As they shift, they cause the mineral liquids to move around. Heat and pressure made the minerals into liquids. The minerals could migrate hundreds of miles before they would harden. They were most likely to harden in cracks, crevices, and the gouges, or the channels, of the earth’s crust. The shifting of tectonic plates formed mountains, hills, rock formations, cliffs, canyons, and valleys. The lead was forced to the earth’s surface, working its way through the cracks and limestone. | |
| Our tri-state area was not glaciated, although the glaciers covered most every other place. The minerals might have either been washed away, or worn away, or covered under tons of glacial rubble and deposits. The mining area was spared from the glacier destruction by only a few miles. The ore deposits occurred in the earth’s layers, some near the earth’s surface and some far below. Because the glaciers didn’t drift over the land around here, it wasn’t scraped flat, and the glaciers didn’t leave behind layers of rock and soil. The minerals remained near the surface of cliffs, and they were easier to find. | |
| The Indians were the first to find the lead in the upper Mississippi. Thousands of white miners came later to mine lead. The upper Mississippi became one of the richest sources of lead ore in the world. In the 1830’s, nearly all of the world’s lead came from here. | |
| Galena is Latin for lead sulfide which is the type of lead found around here. The Galena lead ore is found in a series of rock layers that make up a grouping called Galena Dolomite. To find the lead, the miners would hunt for a crossing, or a place where one vein of ore crossed another. The biggest veins ran east and west and were called “Easts and Wests.” Horizontal veins were known as “gash veins.” Lead also occurs in sheet formations. Most of the sheet formations ran north and south. “Quarterings” were formations that crossed the east and west diagonally. Lead veins always crossed each other and that is what the miners looked for. | |
| Another important mineral, zinc, was found here around the 20th century. It was found 150-300 feet underground. When the lead became harder to find, miners began to find zinc. The miners had tally boards to tell how much zinc that they had mined. They earned around $2.00-2.56 a day. Unlike lead, all the rocks dug out of a zinc mine were brought to the surface before they were sorted. Because of this, zinc mining left large piles of mine tailings. Some of these tailing piles can still be seen in the area, although many of them have been cleared away because they could be environmentally hazardous when dissolved by rain water. | |
| Lead and zinc were resources that brought many people to this area. | |
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Bibliography Schoenhard, Carl B. Jr.
Galena, Hidden Treasure. Galena, Illinois: Carol B.
Schoenhard, Jr., 1988. |
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