The Spruce Pine pegmatite district, a northeastward-trending belt 25 miles
long and 10 miles wide, lies in parts of Avery, Mitchell, and Yancey Counties in the Blue Ridge Province of western North Carolina. The most abundant
rocks in the district are interlayered mica and amphibole gneisses and schists, all of which are believed to be of Precambrian age. These rocks are cut by small bodies of dunite and associated rocks of Precambrian (?) age, large bodies of alaskite and associated pegmatite of early Paleozoic age, and basaltic and diabasic dikes and sills of Triassic (?) age. The rocks of the district have been weathered to saprolite that is locally 50 feet thick.
The major structure in the area is a southwestward-plunging asymmetrical
synclinorium that has its steeper limb on the northwest side.
Feldspar, muscovite as sheet and scrap (ground) mica, and kaolin from the
alaskite and associated pegmatite account for over 90 percent of the total
mineral production of the district. Amounts of other pegmatite minerals,
including quartz, beryl, columbite-tantalite, rare-earth and uranium minerals
are an extremely small part of the mineral resources. Actual or potential
products from other rocks are olivine, vermiculite, asbestos, talc, chromium and nickel, soapstone, mica schist, garnet, kyanite, dolomite marble, and construction materials.