Data / Mines / Diatomaceous earth (diatomite)
Diatomaceous earth (diatomite) mines in the US
Updated November 6, 2026. Source: US Department of Labor, Mine Safety and Health Administration (MSHA), Open Government Data Sets.
MSHA lists 12 open diatomaceous earth (diatomite) mines in the US, run by 5 operators and employing 660 people. Since January 1, 2022 its inspectors issued 483 citations and orders there with $527,674 in proposed penalties, and operators reported 38 injury or illness cases. The operators with the most open mines are U.S. Silica Company, LLC; Imerys Filtration Minerals, Inc.; Dicalite Minerals LLC. Data from MSHA, November 6, 2026.
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- Open mines
- 12
- Operators
- 5
- Employees
- 660
- Active
- 11
- Intermittent
- 1
- Citations and orders since January 1, 2022
- 483
- Significant and substantial
- 100 (20.7%)
- Closure orders
- 6
- High negligence or reckless
- 44
- Proposed penalties
- $527,674
- Amount paid so far
- $519,707
- Inspections
- 167
- Inspector hours on site
- 1,735
- Citations per inspection
- 2.89 (all mines 2.30)
- Accident reports
- 41
- Injury and illness cases
- 38
- Fatalities
- 0
- Latest MSHA record
- November 4, 2026
Operators with the most open mines
Ranked by open mines, then by citations. Sole proprietors and individuals are not listed.
| Operator | Open mines | Employees | Citations since 2022 | Proposed penalties | Injury cases |
|---|---|---|---|---|---|
| U.S. Silica Company, LLC | 6 | 365 | 129 | $57,919 | 19 |
| Imerys Filtration Minerals, Inc. | 3 | 224 | 261 | $451,154 | 15 |
| Dicalite Minerals LLC | 1 | 53 | 38 | $7,101 | 4 |
| Grefco Minerals LLC | 1 | 15 | 36 | $4,504 | 0 |
| Pure Mountain LLC | 1 | 3 | 19 | $6,996 | 0 |
Operators with the most citations
Citations and orders issued since January 1, 2022 at their open mines here.
| Operator | Open mines | Employees | Citations since 2022 | Proposed penalties | Injury cases |
|---|---|---|---|---|---|
| Imerys Filtration Minerals, Inc. | 3 | 224 | 261 | $451,154 | 15 |
| U.S. Silica Company, LLC | 6 | 365 | 129 | $57,919 | 19 |
| Dicalite Minerals LLC | 1 | 53 | 38 | $7,101 | 4 |
| Grefco Minerals LLC | 1 | 15 | 36 | $4,504 | 0 |
| Pure Mountain LLC | 1 | 3 | 19 | $6,996 | 0 |
Mines with the most citations
Open mines, ranked by citations and orders since January 1, 2022.
| Mine | Operator | County | Main commodity | Employees | Citations since 2022 |
|---|---|---|---|---|---|
| Imerys Lompoc Plant | Imerys Filtration Minerals, Inc. | Santa Barbara County, CA | Diatomaceous earth (diatomite) | 198 | 249 |
| Colado Plant | U.S. Silica Company, LLC | Pershing County, NV | Diatomaceous earth (diatomite) | 140 | 42 |
| Dicalite Minerals | Dicalite Minerals LLC | Shasta County, CA | Diatomaceous earth (diatomite) | 53 | 38 |
| Clark Operations | U.S. Silica Company, LLC | Storey County, NV | Diatomaceous earth (diatomite) | 62 | 37 |
| Grefco Mine & Mill | Grefco Minerals LLC | Nye County, NV | Diatomaceous earth (diatomite) | 15 | 36 |
| De-source | Pure Mountain LLC | Malheur County, OR | Diatomaceous earth (diatomite) | 3 | 19 |
| Fernley Operations | U.S. Silica Company, LLC | Churchill County, NV | Diatomaceous earth (diatomite) | 57 | 17 |
| Celatom Plant | U.S. Silica Company, LLC | Malheur County, OR | Diatomaceous earth (diatomite) | 53 | 17 |
| Colado Mine | U.S. Silica Company, LLC | Pershing County, NV | Diatomaceous earth (diatomite) | 36 | 14 |
| Fernley Plant | Imerys Filtration Minerals, Inc. | Lyon County, NV | Diatomaceous earth (diatomite) | 16 | 6 |
| Quincy WA Mine | Imerys Filtration Minerals, Inc. | Grant County, WA | Diatomaceous earth (diatomite) | 10 | 6 |
| Celatom Mine | U.S. Silica Company, LLC | Malheur County, OR | Diatomaceous earth (diatomite) | 17 | 2 |
States
| State | Open mines | Share |
|---|---|---|
| Nevada | 6 | 50% |
| Oregon | 3 | 25% |
| California | 2 | 16.7% |
| Washington | 1 | 8.3% |
Citations and injury cases by year
Calendar years since 2022; 2026 runs to the date of the MSHA files.
| Year | Citations and orders | Significant and substantial | Proposed penalties | Injury and illness cases |
|---|---|---|---|---|
| 2022 | 89 | 22 | $43,615 | 12 |
| 2023 | 79 | 18 | $133,979 | 7 |
| 2024 | 125 | 23 | $215,579 | 8 |
| 2025 | 82 | 14 | $44,528 | 5 |
| 2026 | 108 | 23 | $89,973 | 6 |
Standards cited most at diatomaceous earth (diatomite) mines
Sections of Title 30 of the Code of Federal Regulations named on the citations, with the part each belongs to.
| Standard | What the part covers | Citations |
|---|---|---|
| 30 CFR 56.14107 | Surface metal and nonmetal mines | 36 |
| 30 CFR 56.20003 | Surface metal and nonmetal mines | 35 |
| 30 CFR 56.12032 | Surface metal and nonmetal mines | 34 |
| 30 CFR 56.16001 | Surface metal and nonmetal mines | 33 |
| 30 CFR 56.12004 | Surface metal and nonmetal mines | 33 |
| 30 CFR 56.14112 | Surface metal and nonmetal mines | 31 |
| 30 CFR 56.14100 | Surface metal and nonmetal mines | 26 |
| 30 CFR 47.41 | Hazard communication | 21 |
| 30 CFR 56.4201 | Surface metal and nonmetal mines | 15 |
| 30 CFR 56.11001 | Surface metal and nonmetal mines | 14 |
| 30 CFR 56.18002 | Surface metal and nonmetal mines | 13 |
| 30 CFR 56.12008 | Surface metal and nonmetal mines | 12 |
| 30 CFR 56.12028 | Surface metal and nonmetal mines | 10 |
| 30 CFR 56.12018 | Surface metal and nonmetal mines | 10 |
| 30 CFR 56.14207 | Surface metal and nonmetal mines | 10 |
Injury and illness cases at diatomaceous earth (diatomite) mines
Accident reports by degree of injury, as the operator reported them to MSHA.
| Degree | Cases |
|---|---|
| Permanent disability | 2 |
| Days away from work or restricted activity | 27 |
| No lost time, or an occupational illness | 9 |
What the accident reports at diatomaceous earth (diatomite) mines describe
Accident classification, as MSHA codes the circumstances that contributed most directly.
| Classification | Reports |
|---|---|
| Handling of materials | 11 |
| Slip or fall of person | 10 |
| Machinery | 5 |
| Powered haulage | 3 |
| Other | 3 |
| Handtools (nonpowered) | 2 |
| Electrical | 1 |
| Impoundment | 1 |
| Disorders (repeated trauma) | 1 |
| Fire | 1 |
Equipment named in accident reports at diatomaceous earth (diatomite) mines
| Equipment | Reports |
|---|---|
| Packaging machine | 3 |
| Bulldozer | 3 |
| Trucks | 2 |
| Hand tools (not powered) | 2 |
| Hoist | 1 |
| Road grader | 1 |
| Ore haulage trucks - off highway trucks | 1 |
| Mine car | 1 |
| Forklift | 1 |
| Hand tools (powered) | 1 |
US government work, public domain. Counts come from the MSHA files published on November 6, 2026. An open mine is one MSHA lists as Active, Intermittent, New Mine, Temporarily Idled or NonProducing; 13,673 were open that day. Citations, penalties, inspections and accident reports run from January 1, 2022. A citation is an inspector's allegation and an operator can contest it; the penalty is the amount MSHA first proposed, before any contest or settlement. An operator is the legal entity MSHA assesses, and a parent company is its controller. Mines run by sole proprietors or by individuals are counted in every total and are not named. This page uses MSHA data and is not endorsed or certified by MSHA. Free to reuse with credit to SpecStream under CC BY 4.0. Spot a wrong value? Write to [email protected] with the link to this page.