Mica — from art to technologyWritten by George Ellison
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“Oh, what is that shiny stuff in the rocks?” someone will ask during any sort of outing. And invariably, someone in the group will reply, “Oh, that’s just mica.”
I think to myself, “How could anything so pretty be ‘just mica?’”
Mica lives up to its name, which is derived from the Latin micare: to shine or glitter. The ancient Hindus knew all about mica — four thousand years ago they used it for decorative effects. If you were an ancient Hindu looking for a little glitz in your life, mica was the ideal medium. It was the surface of choice for mythological scenes. The Hindus believed mica crystals are preserved flashes of lightning.
On the other hand, geologists believe micas are prominent rock-forming constituents of igneous and metamorphic rocks that belong to a group of complex aluminosilicate minerals having sheet or plate-like structures formed from flat six-sided crystals with cleavage parallel to the direction of the large surfaces, which allows them to be split into optically flat films.
The Cherokees used the material as a medium of exchange. Mica from this region has been found throughout eastern North America. In return the Cherokees received shells, copper, suitable stones for spear points, shells, feathers, and numerous other commodities. The Indians used it for ornamental and ritualistic purposes. Sacred birds, dancing bears, and serpents with horns were crafted from sheet mica. It was the material of choice throughout eastern North America for centuries — and the Cherokees had mineral rights.
A mica book is so-named because of the resemblance of the cleavage plates of a large crystal to the leaves of a book. The plates can be readily separated into thin sheets with specific thicknesses. Quality sheet mica is graded into 10 classifications. Books flawed with excess inclusions, cracks, or folds are ground into commercial products: coating for roof shingles and cement blocks; paint and rubber additives; and so on, ad infinitum.
The center of mica production in Western North Carolina has traditionally been in the Spruce Pine area. But there were also less extensive mining operations throughout the region, especially in Jackson and Macon counties. In The History of Jackson Country (1987), John L. Bell noted that mica deposits were first discovered “on the road between Webster and Franklin” in 1858. As recently as the early 1940s, “the defense needs during World War II caused a boom in mica,” then very “important in the production of electronic vacuum tubes.” Ninety-four mines were opened in 1942 that “produced 94,943 pounds of sheet and 183,00 pounds of scrap mica. The largest operations were at the Buchanan, Big East Fork, Jasper, Frady, Engle, Cope, Kolb, Tilley, and Stillwell mines.”
Before mica mining became an industrial enterprise in WNC, it was a cottage industry. In The French Broad (1965), one of my favorite books, Wilma Dykeman described those days:
“A large part of this mining is done in small operations — ‘groundhog holes,’ the local people call them, penetrating the sides of hill after hill in these counties … and the raw wound of many an abandoned digging gapes on the mountainside, giving the country an appearance different from the rest of the French Broad watershed.”
Dykeman noted that it was during the post-Civil War era — “when a northern traveler happened to see a large sheet of ‘isinglass’ in one of the cabins, where he stopped overnight “ —that the sheet-mica business was initiated, thereby supplying “practically all of the isinglass used in the old-fashioned stove windows in this country or Canada.”
Isinglass is one of the minerals in the mica group. Sometimes called “white mica,” it occurs in thin transparent sheets. I have been told that after the men had extracted blocks (lenses) of mica from “groundhog holes,” the women took over and separated the fragile sheets of isinglass with their more nimble fingers.
From now on, each time you spot a sparkling cluster of “that shiny stuff in the rocks,” I suspect you’ll think about the ancient Hindu belief that mica crystals are “preserved flashes of lightning.”