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The US produced more than 1.4 billion tons of crushed stone in 2020.
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LimestoneLast week I visited a local limestone quarry with a science camp. Limestone is a sedimentary rock that is formed under water and made from minerals of calcite (calcium carbonate). Look at the quarry wall to see the sedimentary layers. |
Crushed StoneAfter blasting (see video below), the rock is fed through crushers and conveyors to break and sort the rock into different shapes. We are standing next to a pile of #57 rock, which a mix of rock from 0.75 to 1.5 inches across and a common size used in roads and concrete. |
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And Fossils!Some of the layers of limestone in this quarry also contain fossils. There are brachiopods with their two shells, circular crinoid stems, coiled nautiloids, and horn corals like the two in this specimen. |
From "boom" to ballast in seconds
Quarries begin by blasting rock with explosives, or what they call a "shot". A hole is drilled down into the rock to place the explosives. The detonations are timed fractions of a second apart from each other. This better fractures the rock and keeps it from flying dangerously far. Once the dust settles (literally!), the trucks move in and begin scooping, loading, and adding stone to the crushers. It's a pretty impressive turnaround.
Check out this great video that shows the real-time speed and then slow-motion of a quarry shot in Ireland.
Check out this great video that shows the real-time speed and then slow-motion of a quarry shot in Ireland.
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