Recent Publications from the Mineral Resources Program

by Greg D. Marquis, PG

Aggregate is essential to maintaining existing infrastructure and supporting new construction, making it a resource of critical economic importance. Because aggregate is a low unit-value, high-bulk-weight commodity, it must be sourced close to where it is used to reduce transportation-related economic and environmental costs. When nearby sources are unavailable transportation costs can quickly exceed the value of the material and result in increased construction costs, fuel consumption, greenhouse gas emissions, air pollution, traffic congestion, and road maintenance.

Map Sheet 52 is a statewide overview of projected future aggregate needs and currently permitted reserves. The map shows the projected years of permitted reserves remaining, and highlights regions where fewer than ten years of permitted aggregate supply remain. The current estimates of permitted aggregate reserves, aggregate demand, and years of permitted reserves remaining are based on conditions as of January 1, 2024.

To download this release, visit the Aggregate Sustainability in California web page.

by Catherine Wesoloski, PG; Max Garvue; and Erica Key, PG

Map Sheet 68 is a 1:24,000-scale map of the geology of the western Cady Mountains, a potential source of critical minerals. The mapped area covers 55 square miles (142 square km). The project also produced three new Ar/Ar dates and 19 geochemical analyses.

Download Map Sheet 68 as a PDF (45 MB - opens new tab).

by Ben Parrish, PG and Amy Tuzzolino, PG

The California Geological Survey's Mineral Resources Program conducted geochemical reconnaissance sampling of laterite and associated ultramafic rocks in Del Norte County as part of its statewide geochemical reconnaissance initiative. The goal of the sampling program is to collect data that will support current and future critical-mineral, precious-metal, base-metal, and industrial-mineral activities in California. Critical minerals as defined by the U.S. Department of Interior are mineral resources that are essential to our economy and national security and are at risk for supply disruption. The Del Norte County laterite deposits have historically been mined for nickel, cobalt, and chromium.

Samples from laterite and ultramafic rocks of the Josephine Ophiolite in Del Norte County were collected for geochemical analyses. Samples were selected to evaluate trace-element signatures and distribution in laterite deposits and compare trace-element concentration in underlying ultramafic rocks. Samples were also selected to evaluate laterite enrichment processes for nickel, cobalt, and chromium in these deposits.

To download this release, visit the Data Releases web page.

by Greg D. Marquis

California remained one of the largest producers of non-fuel minerals in the United States in 2022. This report discusses the commodities produced as well as production and trends for many commodities.

To obtain the full report, visit the California Mineral Production web page.

by Greg D. Marquis

This report documents the data and procedures used by the California Department of Conservation, California Geological Survey (CGS) to develop the 2024 radon potential zone map for western Nevada County (Plate 1). The CGS produced the map for the California Department of Public Health-Indoor Radon Program through an interagency agreement. The findings provided in this report are based on the association between indoor radon in homes and the underlying geology. The report includes radon potentials for individual geologic units using the percentage of indoor radon measurements ≥ 4.0 picocuries per liter.

Special Report 258 and its associated plate (map) are available as free downloads at the Department of Conservation's File Request application.

Radon is a naturally occurring radioactive gas that is invisible and odorless. Breathing air with elevated levels of radon gas results in an increased risk of developing lung cancer. Learn more about radon.

by Greg D. Marquis

This report documents the data and procedures used by the California Department of Conservation, California Geological Survey (CGS) to develop the 2024 radon potential zone map for western El Dorado County (Plate 1). The CGS produced the map for the California Department of Public Health-Indoor Radon Program through an interagency agreement. The findings provided in this report are based on the association between indoor radon in homes and the underlying geology. The report includes radon potentials for individual geologic units using the percentage of indoor radon measurements ≥ 4.0 picocuries per liter.

Special Report 256 and its associated plate (map) are available as free downloads at the Department of Conservation's File Request application.

Radon is a naturally occurring radioactive gas that is invisible and odorless. Breathing air with elevated levels of radon gas results in an increased risk of developing lung cancer. Learn more about radon.

California remained one of the largest producers of non-fuel minerals in the United States in 2020. This report discusses the commodities produced as well as production and trends for many commodities.

To obtain the full report, visit California's Non-Fuel Mineral Production web page.

by Greg D. Marquis

• Special Report 253 - Mineral Land Classification: Portland Cement Concrete Aggregate in the Western Ventura County and Simi Production-Consumption Regions
• Plate 1 - Mineral Resource Zone Map
• Plate 2 - Resource Sector Map

Summary of SR 253

SR 253 is the second update Mineral Land Classification (MLC) report for Portland cement concrete (PCC) aggregate in Ventura County. The original MLC report was published as SR 145 in 1981. The first update was published as Open-File Report 93-10 in 1993. SR 253 reevaluates PCC aggregate resources, permitted reserves, past production, and includes an updated 50-year projection (through the year 2067) of demand for PCC and all other grades of construction aggregate in the Western Ventura-Simi Production-Consumption Regions.

The following list summarizes some of the major findings and conclusions reached in this update report:

• Of the 27,179 acres of Designated Sectors in the WVS P-C Regions, 1,674 acres (6.2 percent) were lost due to land uses incompatible with mining.
• There are an estimated 5,593 million tons of PCC resources in the WVS P-C Regions. 118 million tons are currently permitted.
• The 118 million tons of permitted PCC aggregate reserves could last less than 23 years.
• The WVS P-C Regions PCC aggregate reserves are approximately 80 percent fine and 20 percent coarse.
• Approximately 25 percent of aggregate (coarse PCC aggregate) was imported to the WVS P-C Regions in 2017.
• Imports to the WVS P-C Regions are transported at least 40 miles, which increases costs and greenhouse gas emissions.
• Barriers to future mine permitting include housing, parks, environmental policies and land use decisions protecting wildlife habitat.

by Ronald K. Churchill, Joshua A. Goodwin, and Brenda L. Callen

This report summarizes indoor radon data available up to 2018 for each county in the state of California, using information provided by the California Department of Public Health through an interagency agreement. The report is available as a single PDF file, which can be viewed using Adobe Acrobat Reader. Follow this link to download Special Report 247.

NOTE: Clicking the link above will take you to our File Request system, where you will need to provide your email address; other than that the process is quick, and you receive a file link within five minutes of requesting it.

For more information about indoor radon in California, visit our Indoor Radon page.

by David Reioux, Benjamin Parrish, Brian J. Swanson, and Howard J. Brown

The California Geological Survey (CGS) released four new preliminary geologic maps, supported by the United States Geological Survey's (USGS) Earth Mapping Resource Initiative (Earth MRI) within the Mountain Pass Rare Earth Element Focus Area. The maps are:

• Preliminary geologic map of the Crescent Peak 7.5-minute quadrangle, New York Mountains, San Bernardino County, California
• Preliminary geologic map of the Castle Peaks 7.5-minute quadrangle, New York Mountains, San Bernardino County, California
• Preliminary geologic map of the Ivanpah 7.5-minute quadrangle, New York Mountains, San Bernardino County, California
• Preliminary geologic map of the Pinto Valley 7.5-minute quadrangle, New York Mountains, San Bernardino County, California

Project Background

In 2019, the CGS entered into a cooperative agreement with the USGS to conduct geologic mapping of the New York Mountains at 1:24,000 scale. This project is supported in part by funding from the USGS and occurs within the Mountain Pass Rare Earth Element Focus Area. The field area was selected due to its proximity to the world class, carbonatite-hosted, light rare earth deposit at Mountain Pass.

Rare earth elements are among 50 minerals listed as critical by the USGS. Critical minerals are defined as being essential for manufacturing products significantly important to the economy and national security and as having supply chains vulnerable to outside disruption. The Earth MRI Project aims to gather information to identify potential domestic sources of critical minerals.

Downloadable Files Related to this Release

The maps are available as PDF files, which can be viewed using Adobe Acrobat Reader. To download these maps, visit our Preliminary Geologic Maps page.

by Catherine Wesoloski, David Reioux, and Brenda Callen

• Special Report 254 - 2021 Update of the Mineral Land Classification for Portland Cement Concrete Aggregate Resources in the San Fernando Valley and Saugus-Newhall Production-Consumption Regions
• Plate 1 - Mineral Resource Zone Map
• Plate 2 - Resource Sector Map

Summary of SR 254

This report, Special Report (SR) 254, serves as an update to the findings presented in SR 143 parts I, II (Anderson and others, 1979), and V (Joseph and others, 1987) and Open-File Report (OFR) 94-14 (Miller, 1994). It includes: 1) a reevaluation of Portland cement concrete (PCC) aggregate resources within the San Fernando Valley and Saugus-Newhall Production-Consumption (P-C) Regions; 2) estimates for the quantity of resources as of December 2018; and, 3) a 50-year forecast of PCC aggregate demand within the San Fernando Valley and Saugus-Newhall P-C Regions from 2018 to 2068.

The major findings are:

• No new sectors were added; the four sectors classified in the San Fernando Valley P-C Region and the three sectors classified in the Saugus-Newhall P-C Region were maintained from SR 143 and OFR 94-14.
• The projected 50-year PCC aggregate demand on the San Fernando Valley P-C Region through the year 2068 is estimated to be 959 million tons.
• The projected 50-year PCC aggregate demand on the Saugus-Newhall P-C Region through the year 2068 is estimated to be 80 million tons.
• Reserves are proprietary but will be exhausted in less than 10 years in both regions if the current demand is sustained.
• Approximately 416 million tons of resources underlie the San Fernando Valley P-C Region.
• Approximately 10.5 billion tons of resources underlie the Saugus-Newhall P-C Region.
• If no additional reserves become available, both the San Fernando Valley and Saugus-Newhall P-C Regions will remain dependent on external sources of PCC aggregate.

by Greg Marquis

• Mineral Land Classification of the Teichert Shifler Property, Yolo County, California, for Portland Cement Concrete Aggregate (2.5 MB PDF)

Background of Special Report 255

Teichert Materials submitted a petition dated September 30, 2020 to the SMGB for classification of the Shifler Property, located approximately three miles west of the town of Woodland in Yolo County, just south of Cache Creek. The property consists of two parcels totaling 442 acres. The project area comprises 277 acres. The project area was most recently classified in CGS Special Report (SR) 245 in 2018. Portions of the project area were classified in SR 245 as not having significant mineral resources based on an analysis of surficial geologic mapping. Under the provisions of the Surface Mining and Reclamation Act of 1975 (SMARA; Public Resources Code § 2712 et seq.), the petitioner requested that the State Geologist reclassify the project area as MRZ-2 for PCC aggregate.

Summary of Special Report 255

The State Geologist investigated the area proposed for mining, and subsequently reclassified it as Mineral Resource Zone 2 (MRZ-2) for Portland cement concrete (PCC) aggregate. The petition contains drill logs that show the presence of construction aggregate at mineable depths throughout the project area. The petition also references a third-party laboratory that concluded the project area aggregate was suitable for use in PCC based on petrographic analysis. In addition to evidence provided in the petition, adjacent properties—also located off-channel from Cache Creek—are being or have been mined for PCC aggregate. The value of the aggregate resource in the project area exceeds the threshold for a significant deposit of construction materials for the purpose of classification.

by Benjamin Parrish

• Special Report 252 - 2021 Update of the Mineral Land Classification for Concrete Aggregate Resources of Merced County, California
• Plate 1 - Mineral Resource Zone Map
• Plate 2 - Resource Sector Map

Clicking the links above will take you to our File Request system, where you can request high-quality PDF versions of the documents. You will need to provide your email address, but other than that the process is quick, and you receive a file link within five minutes of requesting it.

by Erica Key

• Special Report 251 - 2021 Update of the Mineral Land Classification for Construction Aggregate Resources in the Monterey Bay Production-Consumption Region
• Plate 1 - Mineral Resource Zone Map
• Plate 2A - Resource Sector Map 1 of 2
• Plate 2B - Resource Sector Map 2 of 2

Clicking the links above will take you to our File Request system, where you can request high-quality PDF versions of the documents. You will need to provide your email address, but other than that the process is quick, and you receive a file link within five minutes of requesting it.