The Weyerhauser Mine consists of a series of shafts and small dumps in the NW 1/4SE 1/4Sec. 12(Shafts #1, #2 and #3) and in the SW 1⁄4 SW 1⁄4 Sec. 11 (the F Shaft) T. 43N. R.10W. The main dump and shafts #2 and #3 are located just southwest of Shaft #1 on the south side of the Dingle Creek, a tributary to the Ounce River. The rock is mineralized meta-basalt of Keweenawan age (1.1 billion years old) and quite similar to the rock hosting the large native copper ore deposits of northern Michigan. The deposit was discovered in the late 1890’s. Development work continued at the Weyerhauser Mine in 1906‐1914 with shafts, trenching and drilling. F Shaft, for example, was sunk 300 feet and has 4 levels. Even so, no more than a few thousand pounds of ore were produced. Renewed investigation by the U.S. Bureau of Mines occurred in the 1940’s, at the behest of U.S. Senator “Fighting Bob” Lafollette. Shaft #3 was dewatered and many samples were analyzed. The Bureau's study concluded that the ore, though rich in spots, was too erratic in its distribution to warrant further investigation. The only recent activity is the use of the dump rock for crushed stone.

Minerals found in the mine and on the mine dumps include copper, silver, bornite, malachite, azurite, calcite, quartz, chlorite, epidote, prehnite, K feldspar, plagioclase and augite. The native copper was the primary ore mineral, being found as wires and masses reportedly weighing up to 7 lbs. Malachite and, more rarely, azurite occur as films on the native copper. Calcite is found as white cleavable masses in amygdules. Amygdules and veins often contain white quartz and occasionally some brown agates. Chlorite is abundant as light to dark green soft scaly masses. Epidote id found as masses and small radiating crystal groups in amygdules. Prehnite is particularly common in Shaft #3 dumps where it occurs as white to pale green or pale pink masses, often with a radiating internal structure. The pink color could come from small included flakes of copper. Prehnite forms veins of radiating clusters of crystals about cores of the dark green chlorite or yellow green epidote. K feldspar (adularia) occurs as pink to orange grains in amygdules. Plagioclase and augite make up the bulk of the diabasic meta-basalt which is the matrix for the veins and amygdules.

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Link to USGS MRDS:	10082586

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References