DIATOMITE

Diatomite is a chalk-like, soft, friable, very-finegrained, siliceous sedimentary rock. Typically light in color (white if pure, commonly buff to gray in situ), diatomite is also very finely porous, very low in density, and essentially chemically inert. Diatomaceous earth is a common alternate name, but the term is more appropriate for unconsolidated or less lithified rock of the same origin. Diatomite deposits accumulate in oceans or fresh waters from the cell walls of diatoms, composed of amorphous hydrous silica. Diatoms are microscopic, single-celled organisms, often appearing as colonial aquatic plants (algae). Diatom cells contain an elaborate internal siliceous skeleton. More than 10,000 living diatom species have been identified, in addition to another 10,000 known diatom fossil forms. Production, exports and imports Diatomite deposits are usually mined as openpit operations. If necessary, the mined crude ore is dried and crushed. Dried diatomite is collected in cyclones and fed through air separators to remove coarse material and impurities. Calcination and flux calcination are used to thermally volatilize organic material and oxidize iron. Calcination also is used to increase diatomite hardness, specific gravity and refractive index. The fusing of small diatomite particles into clusters can also be accomplished through calcination, which results in increased pore size and volume. Diatomite products are sold as various grades of calcined powders. The United States continues to be the world’s leading producer and consumer of diatomite. Production of diatomite in the United States during 2023 was estimated to be 830 kt (910,000 st), essentially unchanged from 827 kt (910,000 st) in 2022. Six companies operated 12 mines and nine processing facilities in California, Nevada, Oregon and Washington. According to the U.S. Census Bureau, U.S. diatomite exports were 53.4 kt (58,900 st). Imports were lower at 11.6 kt (12,800 st). Total world production of diatomite was an estimated 2.6 Mt (2.9 million st) in 2023. Following the United States, other significant diatomite producers in 2023 were Denmark (440 kt or 490,000 st), China (270 kt or 300,000 st), Turkey (210 kt or 230,000 st), and Argentina, Mexico and Peru (each with 100 kt or 110,000 st). World resources of crude diatomite appear to be adequate for the foreseeable future. However, increased transportation costs may encourage the development of sources of material closer to markets. Prices The unit value of diatomite varied widely by end use in 2023. The estimated annual average unit value of diatomite in 2023 was $410/t ($370/st), essentially unchanged from 2022. Diatomite used as an absorbent and as a lightweight aggregate in cement was priced at about $10/t ($9/st), but specialty grade diatomite, used in art supplies, biomedical applications or cosmetics, could be priced more than $1,000/t ($900/st). Consumption Domestic apparent consumption in 2023 was estimated to be 780 kt (860,000 st). The internal structure and inert chemical composition of diatomite make it an excellent raw material for filtration, absorbent and filler applications. Filtration, especially the purification of beer, liquors and wine, and the cleansing of greases and oils continued to be the largest end use for diatomite. Other applications included the removal of microbial contaminants, such as bacteria, protozoa and viruses, from public water systems. The use of diatomite as a filler, which serves to displace higher-cost raw materials, and in pharmaceutical applications, including the filtration of human blood plasma, continues to increase, as has its use as an insecticide base and in cement and concrete pozzolan. In 2023, approximately 50 percent of diatomite was utilized in filter aids. The remaining 50 percent was used in abrasives, absorbents, cement, fillers, insulation, lightweight aggregates and other unspecified uses. A small amount, less than 1 percent, was used for specialized biomedical and pharmaceutical purposes. Substitutes Many materials can be substituted for diatomite, especially for lightweight aggregates purposes, such as expanded perlite and silica sand. Synthetic filters, including ceramic, polymeric or carbon membrane, and cellulose fibers offer competition as filter media. Alternate filler materials include clay, ground limestone, mica, perlite, silica sand, talc and vermiculite. For thermal insulation purposes, materials such as specialty brick, various clays, mineral wool, expanded perlite and exfoliated vermiculite may be used. Many alternatives exist for diatomite as a pozzolan, but its use as an ingredient of portland cement has increased in recent years. The encroachment of natural and synthetic substitute materials into diatomite markets has not been significant. Outlook Adequate supplies of diatomite are likely to remain available for the foreseeable future. The economic stability of the diatomite industry was largely owing to its use as a filtration medium, where demand remains strong and is not sensitive to economic cycles. This is particularly so in the filtration of spirits, as well as human blood plasma and other biotechnical applications. Likewise, the substitution for diatomite by more advanced filtration products, including carbon membranes, ceramics and polymers, was not a concern in 2023. The high costs associated with these alternatives and a cultural preference toward the use of diatomite in the brewing and wine industries indicate a strong likelihood for the continued widespread use of diatomite in filtration. Reference U.S. Geological Survey, 2024, Mineral Commodity Summaries 2024—Diatomite: U.S. Geological Survey, p. 68–69, https://pubs.usgs.gov/periodicals/mcs2024/mcs2024.pdf.

DIATOMITE

Authored by:
R.D. Crangle Jr

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

CONSTRUCTION AGGREGATES

DIMENSION STONE

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