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Sandstone

November 19, 2008

Sandstone is a sedimentary bedrock composed mainly of sand-size mineral or bedrock grains. A lot of sandstone is composed of quartz and/or feldspar because these are the a lot of accepted minerals in the Earth’s crust. Like sand, sandstone may be any color, but the a lot of accepted colors are tan, brown, yellow, red, gray and white. Since sandstone beds generally anatomy awful arresting cliffs and added topographic features, assertive colors of sandstone accept been acerb articular with assertive regions.

Some sandstones are aggressive to weathering, yet are simple to work. This makes sandstone a accepted architecture and paving material. However, some that accept been acclimated in the past, such as the Collyhurst sandstone acclimated in the arctic of England, accept been begin beneath resistant, necessitating adjustment and backup in earlier buildings. Because of the acerbity of the alone grains, accord of atom admeasurement and friability of their structure, some types of sandstone are accomplished abstracts from which to accomplish grindstones, for cutting blades and added implements. Non-friable sandstone can be acclimated to accomplish grindstones for cutting grain, e.g., gritstone.

Rock formations that are primarily sandstone usually acquiesce aperture of baptize and are absorptive abundant to abundance ample quantities, authoritative them admired aquifers. Fine-grained aquifers, such as sandstones, are added apt to clarify out pollutants from the apparent than are rocks with cracks and crevices, such as limestone or added rocks burst by seismic activity.

limestone

November 17, 2008

limestone sedimentary rock wholly or in large part composed of calcium carbonate. It is ordinarily white but may be colored by impurities, iron oxide making it brown, yellow, or red and carbon making it blue, black, or gray. The texture varies from coarse to fine. Most limestones are formed by the deposition and consolidation of the skeletons of marine invertebrates; a few originate in chemical precipitation from solution. Limestone deposits are frequently of great thickness. The action of organic acids on underground deposits causes such formations as the Luray Caverns, the Carlsbad Caverns, and Mammoth Cave. Limestone is used as a flux in the extraction of iron, as an ingredient in Portland cement, as a source of lime