MICA

Mica has several unique physical properties. The crystalline structure of mica forms layers that can be split or delaminated into thin sheets. These sheets are chemically inert, dielectric, elastic, flexible, hydrophilic, insulating, lightweight, platy, reflective, refractive, resilient, and range in opacity from transparent to opaque. Mica is stable when exposed to electricity, light, moisture and extreme temperatures. The mica group represents 37 phyllosilicate minerals that have a layered or platy texture. The commercially important micas are muscovite and phlogopite, which are used in a variety of applications. Muscovite is the principal mica used by the electrical industry to make micabased capacitors that can operate in environments with temperatures and/or frequencies that are too high for polypropylene capacitors. Phlogopite mica is used in plastic composites for automotive applications because of its dimensional stability, increased stiffness, and improved heat distortion temperature. Production U.S. mine production of scrap and flake mica was estimated to be 38 kt in 2023, a 10 percent decrease from 2022. Production of ground mica was an estimated 65 kt, compared with 66.3 kt in 2022. Mica was mined in Georgia, North Carolina and South Dakota. Scrap mica was recovered primarily from mica and sericite schist and as a byproduct from feldspar, industrial sand beneficiation, and kaolin. Ground mica was produced from domestic and imported scrap and flake mica. In 2023, world production of scrap and flake mica was estimated to have increased to 330 kt from 318 kt in 2022. China (85 kt), Finland (60 kt), Madagascar (50 kt) and the United States (38 kt) were the leading producers. World production of sheet mica was unavailable in 2023, but India (1 kt) was thought to be the leading producer. Consumption Domestic apparent consumption of all forms of scrap and flake mica was estimated to have been 54 kt in 2023, 11 percent lower than in 2022, owing in part to reduced use in oil and gas drilling and lower imports. Consumption of sheet mica was estimated to have decreased to 3.3 kt in 2023 from 4.6 kt in 2022, owing to a decrease in imports. The leading domestic use of ground mica was in joint compound for filling and finishing seams and blemishes in gypsum wallboard (drywall). The mica acts as a filler and extender, provides smooth consistency, improves the workability of the compound and provides resistance to cracking. The second-ranked use of ground mica was as an additive to drilling muds by the natural-gas and oil well drilling industry. Coarsely ground mica flakes help prevent the loss of circulation by sealing porous sections of the drill hole. Mica was used in paint, where ground mica is used as a pigment extender that also facilitates suspension, reduces chalking, prevents shrinking and shearing of the paint film, increases resistance of the paint film to water penetration and weathering, and brightens the tone of colored pigments. The plastics industry used ground mica as an extender and filler, especially in parts for automobiles as lightweight insulation to suppress sound and vibration. Other significant uses for ground mica are in the rubber industry as an inert filler and mold release compound. As a surface coating in the production of rolled roofing and asphalt shingles, mica prevents the sticking of adjacent surfaces. Mica is used in decorative coatings on wallpaper, concrete, stucco and tile surfaces. Ground phlogopite mica is used in automotive brake linings and clutch plates to reduce noise and vibration (asbestos substitute). Wet-ground mica, which retains the brilliancy of its cleavage faces, is used primarily in pearlescent paints by the automotive industry. In the cosmetics industry, its reflective and refractive properties make mica an important ingredient in blushes, eyeliner, eyeshadow, foundation, hair and body glitter, lip gloss, lipstick, mascara, moisturizing lotions and nail polish. Mica is added to latex balloons to provide a colored shiny surface. Sheet mica is used principally in the electronics and electrical industries. Its usefulness in these applications is derived from its unique electrical and thermal insulating properties and its mechanical properties, which allow it to be cut, punched, stamped and machined to close tolerances. Prices In 2023, the average unit value of scrap and flake mica produced in the United States, which included high-quality sericite, was estimated to be $100/t. The average unit value of dry-ground mica was estimated to be $300/t, and the average unit value of wet-ground mica was estimated to be $350/t. Sheet mica prices vary with grade and can range from less than $1/kg for low-quality mica to more than $2,000/kg for the highest quality. The estimated average unit value of mica splittings consumed in the United States in 2023 was $1.60/kg. Foreign trade According to the U.S. Census Bureau, U.S. imports and exports of scrap and flake mica were 19.4 kt and 3.73 kt, respectively, in 2023. Imports of scrap and flake mica decreased by 14 percent, and exports decreased by 16 percent, compared with 2022. In 2023, China (40 percent), Canada (37 percent) and India (6 percent) supplied most of U.S. imports of scrap and flake mica, with the remainder from several other countries. Most exports of scrap and flake mica went to Mexico (27 percent), Canada (14 percent), and Brazil (16 percent). In 2023, U.S. imports and exports of sheet mica were 4.32 kt and 1.01 kt, respectively. Imports of sheet mica decreased by 20 percent, and exports increased by 26 percent, compared with 2022. In 2023, China (80 percent), Brazil (4 percent) and India (4 percent) supplied most of U.S. imports of sheet mica, with the remainder from several other countries. Most U.S. exports of sheet mica went to Mexico (34 percent), China (11 percent) and Austria (8 percent). Outlook The major markets for ground mica — drywall joint compounds and paints — are mature and relatively stable, with growth tied to housing construction and interest rates. Demand is also affected by automobile production because interior and exterior parts typically contain dry-ground mica or engineered mica composites, and exterior surfaces may be painted with wet-ground pearlescent pigments and mica-containing coatings. Demand for ground mica in smaller specialty markets such as coated micas, cosmetics, nylon and polyester resins, and polypropylene composites, is expected to have an annual growth rate slightly higher than that of the entire ground mica industry. Consumption of block and sheet mica is expected to increase slowly as demand increases in a few specialty markets, such as electronics. A shortage of domestic high-quality block mica is expected to continue because of the generally low percentage of high-quality mica in deposits currently being mined, mostly from pegmatites. Future supplies of all forms of mica are expected to come increasingly from imports, primarily from Brazil, Canada, China, Finland and India. Reference U.S. Geological Survey, 2024, Mineral Commodity Summaries 2024—Mica: U.S. Geological Survey, p. 120–121, https://doi.org/10.3133/mcs2024

MICA

Authored by:
S.M. Jasinski

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MANGANESE

NITROGEN — AMMONIA

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