VERMICULITE

Vermiculite is a hydrated magnesium-aluminumiron silicate mined from shallow surface deposits. Raw vermiculite is similar in appearance to mica and contains water molecules within its internal structure. In a raw state, vermiculite ranges in color from black to various shades of brown to yellow. When vermiculate flakes are heated rapidly to a temperature above 870 °C, the intermolecular water flashes into steam and the flakes expand into gold- or bronzecolored accordion-like particles. This expansion process is called exfoliation, and the resulting ultralightweight aggregate is chemically inert, fire resistant and odorless. Vermiculite was discovered in 1824 by Thomas H. Webb; however the first successful commercial vermiculite mine did not begin production until the 1920s when the Zonolite Co. began mining vermiculite in Libby, MT. Today there are two active vermiculite mining companies in the United States. Vermiculite, which gets its name from the Latin word vermiculare, meaning to breed worms, is mostly mined using openpit mining techniques. Production In 2022 an estimated 100 kt of vermiculite was produced in the United States by Specialty Vermiculite Corp., a subsidiary of Dicalite Management Group Inc., in Enoree, SC, and Virginia Vermiculite LLC in Louisa, VA. Data have been rounded to avoid disclosing company proprietary data. An estimated 80 kt of vermiculite ore was exfoliated in 2022, a 3 percent increase from 78 kt in 2021. Exfoliation was performed by 13 companies located in nine states: Arizona, Arkansas, Illinois, Massachusetts, Michigan, New Jersey, Ohio, Pennsylvania and South Carolina. Consumption Vermiculite concentrate that has not been exfoliated is used primarily in fire protection products, but most vermiculite is consumed in exfoliated form. Exfoliated vermiculite has a wide range of uses because of its attributes, including fire resistance, high liquid-absorption capacity, inertness, low density and low thermal conductivity. Agricultural uses (horticulture, soil conditioning and fertilizer carrier) were estimated to remain the leading uses of exfoliated vermiculite in 2022. When mixed with peat, bark or compost, vermiculite provides excellent aeration and moisture retention as well as promoting fast growth of plants. Other significant uses include aggregates (concrete, plaster and premixes) and insulation (loose-fill, block, high-temperature and packing insulation and sealants). Substitutes Several substitutes can be used in lieu of vermiculite. Expanded perlite, as well as less costly alternatives such as expanded clay, shale slag and slate are substitutes for exfoliated vermiculite in lightweight concrete and plaster. In agriculture, alternate materials include bark and other plant materials, peat, perlite, sawdust and synthetic soil conditioners. Substitutes for loose-fill fireproofing insulation include fiberglass, perlite and slag wool. Foreign trade Trade data for vermiculite concentrate are not collected as a separate category by the U.S. Census Bureau but are included within the group “vermiculite, perlite and chlorites, unexpanded.” An estimated 24 kt of vermiculite valued at $10.3 million was imported into the United States during 2022. Brazil and South Africa accounted for nearly all vermiculite imports. The United States produces finer-grade vermiculite concentrate and relies on imports for coarser than medium-sized concentrate. Exports were estimated to be 8 kt of vermiculite valued at $1.9 million in 2022, with Canada being the leading destination. International Global production of vermiculite was estimated to have increased slightly to 470 kt in 2022 compared with 464 kt in 2021. South Africa continued to be the leading vermiculite producing country, followed, in descending order, by the United States and Brazil. Outlook The worldwide production capacity of vermiculite continues to exceed consumption. However, the production of finer grades of vermiculite have far exceeded that of coarser grades for several decades. Exploration and development of vermiculite deposits containing medium, large and premium grades are likely to continue, while producers are also likely to continue to investigate ways to use the finer grades in higher-value markets. New and innovative uses of vermiculite will continue to be developed. Demand for vermiculite remains strong. With less domestic production, as well as global supply issues, vermiculite exfoliation operations are experiencing difficulties obtaining crude vermiculite, which has led consumers to use substitute materials. One company recently announced it will be substituting perlite for vermiculite in the agricultural products it produces.

VERMICULITE

Authored by:
Kristi J. Simmons

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To view the past issues of the UCA magazine you must be a member of SME/UCA.

VANADIUM

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