Precambrian muscovite from the M. I. C. A. mine, Picuris Mountains, New Mexico
— George S. Austin, James M. Barker, and Paul W. Bauer

The Mineral Industrial Commodities of America (M.I.C.A.) mine is the only domestic muscovite producer west of the Appalachian Mountains. The mine is in quartzofeldspathic muscovite schist that represents strained, metamorphosed, hydrothermally altered rhyolitic flows and/or tuffs of Early Proterozoic age. These schists are probably correlative with the Glenwoody Formation of the Picuris Mountains and other feldspathic schists of the Vadito Group. The orebody consists of a high-grade lower "A" zone and a low-grade upper "B" zone. It ranges in grade from 70-25% muscovite with an average of about 33% over a mined area of 45-75 m by 730 m. The ore is ripped by bulldozers, and moved by front-end loaders to a nearby screening plant. Boulders larger than 10 cm are stockpiled at the mine. Ore that passes through the 10 cm grizzly is crushed to <1.9 cm and shipped 50 km to the mill near Velarde. The ore is processed in a fluid-energy mill and/or a flotation circuit to produce muscovite ranging in size from 1-100 p.m and brightness of 80-90% which can be bleached to over 90%. The finished product is used primarily in joint cements for plasterboard and in paints.