Limberlost, in addition to its sand, gravel and quartz deposits, has a partially mined mica outcrop and various garnet showings.
The mica mine can be located by entering the Limberlost Reserve through the first gate on Limberlost Road, immediately west of Peeler Lake. From the gate, the old mine road heads south for nearly two kilometres before it deteriorates into a rough forest trail.
The mica outcrop, which runs in a north-south direction, is approximately four hundred meters north of Eagle Lake. Mine tailings stretch along each side of the main dyke, piled fifteen to twenty feet high, and in most areas are heavily covered by years of leaf litter. Relatively thick books of mica can still be found in the tailings and unmined sections. From these it is clear that the mine was high-graded, probably in response to the surge in demand arising from the introduction of electronic capacitors and other war time needs in the 1940s.
One of the world’s richest mica mines was discovered and mined directly north of Limberlost near Lake Nippissing. The U.S. government is known to have funded this mine to build its strategic reserves during the Second World War. The mine tailings are predominantly comprised of melon-sized blocks of opaque quartz and pink feldspar, which is used in the manufacture of glass, pottery and enamels.
Even more interesting are the grape-sized garnets that can be found attached to the feldspar and quartz rocks in certain areas of the mine. These are much larger than the garnets found in the shale rocks of the Windy Cave and elsewhere on the reserve. However, these garnets are more fractured than those in the deposit on the north shore of the Limberlost Outpost on Fishtail Lake, which is the largest garnet deposit in Ontario. Garnets are considered to be semiprecious stones, with the purest specimens reserved for jewelry while fractured stones are used for industrial abrasives, including sandpaper.