What's the difference between silt, sand, and gravel? Size. Silt is a naturally occurring granular material .004mm-.0625mm; sand grains are .0625mm-2mm; gravel is 2mm-64mm. Most sands are in the 1mm range. While most sands contain silica (SiO2), sand composition and its resulting color and texture varies widely, including white gypsum sands in New Mexico, black volcanic sands (from basalt and obsidian) in Greece, green olivine sands in Hawaii and Guam, and coral pink sands (from hematite) in Utah.
- Chemistry Daily
Last updated by curious on Sept. 26, 2009
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