Sand Grains: Sand is a particular sediment size range with grains from 1/16 to 2 mm in diameter. Sand is usually made of of a mixtures grain types, some of which can give us information on the sediment history. Quartz is generally the most common constituent of sand. It is derived from the weathering of Granites, Granitoids (granite-like plutonic rocks) , metamorphic rocks, or older sedimnetary rocks. Quartz is very resistent to both mechanical and chemical attack and remains as sand grains after most other minerals have been broken down into smaller particles or dissolved away. In this weeks lab we are looking at a variety of sand types. These are natural samples, so no sample is made up of a single grain type. Many of the samples do have a dominent grain type, however, that can tell us about the history of that sand sample. Quartz grains rolled around in the surf at a beach are polished much like rocks are polished in a rock tumbler. This results in polished sand grains which under the
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