Psammit (from other Greek ψαμμίτης , “sandy”) is a sandy clastic rock , which mainly (more than 50%) consists of fragments with a diameter of 0.5 to 1 mm. A psammite may be cemented sandstone or non-cemented ordinary sand .
Monomineral psammites, usually based on quartz , oligomictic (a mixture of two components, for example, quartz- feldspar ) and polymineral ( arkoses and graywackes ) are distinguished by composition. Psammites are a product of weathering , the subsequent transfer of fragments form a sequence of diverse composition at the borders of mountain regions. On the plains, deposits of psammites have a low thickness and a more uniform composition (quartz and other persistent minerals).
Psammit deposits are valuable as sources of building materials. In addition, they can contain alluvial deposits of gold, platinum, diamonds or can be a reservoir for oil and gas deposits .
Literature
- Psammites // Great Soviet Encyclopedia : [in 30 vols.] / Ch. ed. A.M. Prokhorov . - 3rd ed. - M .: Soviet Encyclopedia, 1969-1978.
| Breed group | Debris size | Uncemented | Cemented | ||
|---|---|---|---|---|---|
| Rounded | Neokatannye | Rounded | Neokatannye | ||
| Coarse rocks ( psephitis ) | 10 - 1 m | Block boulders | Blocks | - | - |
| 1 m - 10 cm | Boulders | Breaks (blocks) | Boulder conglomerate | Breaking (block) breccia | |
| 10 - 1 cm | Pebbles | Crushed stone | Pebble conglomerates | Crushed Breccias | |
| 1 cm - 2 mm | Gravel | Dresva | Gravelites | Gingerbread man | |
| Sand rocks ( psammits ) | 2 - 0.05 mm | Sands | Sandstones | ||
| Dusty rocks (silt) | 0.05 - 0.005 mm | Siltstone | Siltstone | ||
| Clay rocks ( pelite ) | <0.005 mm | Silt , clay | Clays , mudstones | ||