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Aggregate mining on Mount Zion, Clayton, California

Josua A. Goodwin
Aggregate mining on Mount Zion, Clayton, California (in Regional geology of Mount Diablo, California; its tectonic evolution on the North America Plate boundary, Raymond Sullivan (editor), Doris Sloan (editor), Jeffrey R. Unruh (editor) and David P. Schwartz (editor))
Memoir - Geological Society of America (September 2021) 217: 97-103


Two construction aggregate companies, Cemex and Hanson Aggregates, operate respective crushed stone quarries on the east and west slopes of Mount Zion in Clayton, California. These sidehill quarries utilize a single highwall and mine Jurassic diabase of the Coast Range ophiolite that formed as a sheeted dike complex. Hydrothermal veins, some containing 20%-30% disseminated pyrite and chalcopyrite, cut the diabase. The east quarry, operated by Cemex, was started by the Harrison-Birdwell Company in 1947. The west quarry, operated by Hanson, was started by the Henry J. Kaiser Sand and Gravel Company in 1954. The Cemex quarry highwall is visible as you come into the city of Clayton on Marsh Creek Road, with a height of approximately 280 m (920 ft). The height of the highwall at the Hanson quarry is approximately 215 m (700 ft). Both operations remove weathered diabase overburden to expose fresh diabase, which is drilled, blasted, and hauled to the plant for processing. To ensure aggregate is suitable for construction, quality assurance testing is conducted in accordance with the specifications of various agencies. These quarries supply the surrounding area with aggregate for hospitals, schools, highways, dams, and other buildings. Noteworthy projects supplied by the Clayton quarries include the Concord BART Station, Interstate-680, Interstate-580, Calaveras Dam, Sherman Island Levee, Highway 4, Highway 24, and Bay Bridge epoxy asphalt. Before aggregate was mined, Mount Zion was the site of a copper rush from 1862 to 1864. Gold and silver were also reported in various assays from the Clayton district. Although prospecting created excitement around Clayton, no productive orebodies were ever discovered.

ISSN: 0072-1069
Serial Title: Memoir - Geological Society of America
Serial Volume: 217
Title: Aggregate mining on Mount Zion, Clayton, California
Title: Regional geology of Mount Diablo, California; its tectonic evolution on the North America Plate boundary
Author(s): Goodwin, Josua A.
Author(s): Sullivan, Raymondeditor
Author(s): Sloan, Doriseditor
Author(s): Unruh, Jeffrey R.editor
Author(s): Schwartz, David P.editor
Affiliation: California Geological Survey, Sacramento, CA, United States
Affiliation: San Francisco State University, Department of Earth and Climate Science, San Francisco, CA, United States
Pages: 97-103
Published: 20210907
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
ISBN: 9780813782171
References: 16
Accession Number: 2021-060530
Categories: Economic geology, geology of nonmetal deposits
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sect., geol. sketch map
N37°55'00" - N37°55'60", W121°58'00" - W121°55'60"
N37°56'28" - N37°56'28", W121°56'09" - W121°56'09"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2021, American Geosciences Institute.
Update Code: 2021
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