Modern episodes

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One of the oddities of the modern episodes of glaciation is that while threefifths of all the ice in the world covered North America and extended south of Springfield, Illinois, the valley of the Yukon River in and near Alaska was never glaciated, and as a result the gold in the Yukon drainage-the gold of the richest placer streams ever discovered in the world-was left where it lay, and was not plucked up and similarly scattered by overriding ice. Miners in Indiana learned to look in their pans for menaccanite-beanlike pebbles of iron and titanium that signalled with some consistency the propinquity of gold. The flexplek huren den haag menaccanite had come out of the exposed Precambrian core of Canada-the Canadian craton, also known as the Canadian Shield. There were garnets in the gold pans, too-and magnetite, amphibole, corundum, jasper, kyanite. Nothing in that list is native to Indiana, and all are in the Canadian Shield. There is Canadian copper in the drift of Indiana, and there are diamonds that are evidently
Canadian, too. Hundreds have been discovered-pink almondshaped hexoctahedrons, blue rhombic dodecahedrons. Weights have approached five carats, and while that is modest compared with twenty-carat diamonds found in Wisconsin, these Indiana diamonds have nonetheless been accorded the stature of individual appellations: the Young Diamond (1898), the Stanley Diamond (1900). The source of a diamond is a kimberlite pipe, a form of diatreme-a relatively small hole bored through the crust of the earth by an expanding combination of carbon dioxide and water which rises from within the earth’s mantle and moves so fast driving magma to the surface that it breaks into the atmosphere at supersonic speeds. Such events flexplek huren tilburg have occurred at random through the history of the earth, and a kimberlite pipe could explode in any number of places next year. Rising so rapidly and from so deep a source, a kimberlite pipe brings up exotic materials the like of which could never appear in the shallow slow explosion of a Mt. St. Helens or the flows of Kilauea. Among the materials are diamonds. Evidently, there are no diamond pipes, as they are also called, in or near Indiana. Like the huge red jasper boulders and the tiny flecks of gold, Indiana’s diamonds are glacial erratics.

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