sedimentary
Gravel (Crushed Stone Aggregates)
Mixed Siliciclastic / Carbonate Aggregate
Hardness varies by component minerals (typically 3 to 7 on the Mohs scale). Color ranges from dull gray, brown, and tan to greenish tones. Luster is earthy to sub-vitreous, with angular to sub-rounded fragments.
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Physical properties
Hardness varies by component minerals (typically 3 to 7 on the Mohs scale). Color ranges from dull gray, brown, and tan to greenish tones. Luster is earthy to sub-vitreous, with angular to sub-rounded fragments.
Formation & geological history
Formed through natural weathering, erosion, and stream transport of pre-existing igneous, sedimentary, and metamorphic rocks, or produced mechanically by crushing quarried bedrock.
Uses & applications
Widely used as construction aggregate, road base, concrete constituent, railway ballast, and landscaping gravel.
Geological facts
Gravel is one of the most mined materials on Earth. Naturally deposited river gravels played a crucial role in historical gold rushes due to placer deposits.
Field identification & locations
Identified by coarse, loose, sub-angular to rounded rock fragments ranging in size from 2 mm to 75 mm. Found extensively along riverbeds, glacial deposits, beaches, and quarries worldwide.
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