What are sand and gravel? Sand and gravel are defined not by their composition, but by their size. Sand is defined by particles 1/16 to 2 mm in diameter. Gravel is defined by particles greater than 2 mm in diameter. Sand and gravel in Tennessee are composed largely of the mineral quartz - Silicon Dioxide (SiO2).
When and how was it deposited? Sand and gravel are formed from the erosion of rocks containing chert and quartz.
| Quaternary |
| Tertiary |
| Cretaceous |
| Jurassic |
| Triassic |
| Permian |
| Pennsylvanian |
| Mississippian |
| Devonian |
| Silurian |
| Ordovician |
| Cambrian |
| Proterozoic |
Uses of Sand and Gravel? The main uses of sand and gravel are :base for roads, ingredient in concrete, construction fill, covering material (as in school yards), snow ad ice control, abrasives, and fillers.
Very pure sand (SiO2) is used to make glass.
Dredging for sand in a West Tennessee River
from Tennessee Minerals Annual, Bulletin #83 of Tennessee Division of Geology
Environmental consequences of sand and gravel mining. Dredging gravel from rivers loosens a lot of fine sediment along with the sand and gravel, which increases the turbidity (cloudiness) of the water downstream and can be harmful for organisms which live in the river. In some rivers, toxic material is buried in the sediment, and dredging can release it.