Michael Conte, Jr.
Connecticut has within its boundaries the three types of rocks found on the Earth: Igneous, Sedimentary, and Metamorphic. These rocks have spawned many businesses that have been vital to the economy of our state. Igneous rocks form by the cooling and solidification of magma in the crust and of lava on the crust.
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(see diagrams) We tend to find Igneous rocks in places where the Earth has broken through, East Rock, West Rock and outcrops in the Central Valley, An easy way to identify traprock is its black color. It is also possible to find this type of rock with a red coloring in it. This red coloring is actually the rusting of the rock due to its high iron content being exposed to the elements. Areas in the state where you could find samples of these rocks, which were primarily crushed and used for building roads (traprock) would be: Woodbury Traprock Quarry, Pine Rock Quarry and Tilcon Quarry.
Another rock common to Connecticut and used in industry is Sedimentary Rock. These rocks can be made of loose mineral particles deposited on land or in water then compacted and cemented together, e.g. sandstone from sand, shale from mud.
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This type of stone is easily cut for building supplies, is very porous and does not weather well unless properly installed in a wall. A great deal of Portland sandstone was used in buildings in New York City. Connecticut sandstone is easily recognizable due to its high concentration of iron which makes it have a brown appearance. Places to visit are: The Andrews and The Case Quarries in Portland.
Metamorphic Rocks are Igneous and Sedimentary Rocks changed by internal heat, pressure and penetration by fluids without melting. They form deep in the Crust and are later exposed by erosion.
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Examples of Metamorphic Rock in Connecticut are granite, that is found in Stony Creek and marble, found in the highlands of Northwestern Connecticut. Both of these rocks were formed by a change in sandstone. These rocks resist weathering very well and are used a great deal in buildings and curbstones. (The Brooklyn Bridge has facings that came from the Stony Creek Quarry.) Places to visit are: Stony Creek and Cobalt Mines.