Sedimentary
Sedimentary rocks are rocks and minerals made by the force of tiny almost microscopic rocks, called sediments being forced together sometimes with magma as a guide. As you can see in this specimen of Citrine, (bottom right), there are layers of crystals (citrine crystals, quartz, amber, mudstone and sandstone). These layers are key in gem identification for layers are very common in sedimentary rocks.
Sediments carry to different places with wind and water. When the sediments journey is completed over the years it compresses with others and forms new rocks. Rain also can push sediments to different places.
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Sandstone rocks are sedimentary rocks made from small grains of the minerals quartz and feldspar. They often form in layers as seen in this picture. They are often used as building stones. |
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Limestone rocks are sedimentary rocks that are made from the mineral calcite which came from the beds of evaporated seas and lakes and from sea animal shells. This rock is used in concrete and is an excellent building stone for humid regions. |
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Shale rock is a type of sedimentary rock formed from clay that is compacted together by pressure. They are used to make bricks and other material that is fired in a kiln. |
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Conglomerate rocks are sedimentary rocks. They are made up of large sediments like sand and pebbles. The sediment is so large that pressure alone cannot hold the rock together; it is also cemented together with dissolved minerals. |
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Gypsum rocks are sedimentary rocks made up of sulfate mineral and formed as the result of evaporating sea water in massive prehistoric basins. It is very soft and is used to make Plaster of Paris, casts, molds, and wallboards. |
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