BGS Rock Classification Scheme - Text search results
220 records found. Please click on a code for a "thumbnail" definition.
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| Description | Code |
|---|---|
| Pitchstone - A type of glassy-igneous-rock. It is a glassy, altered (hydrated/devitrified), igneous rock. The term has no compositional inference. British Geological Survey Research Report RR/99/06, section 8.3. | PTST |
| Basalt, pyroxene-phyric | PXPBA |
| Pyroclastic-rock, basaltic | PYBA |
| Pyroclastic-breccia, basaltic | PYBRB |
| Sapropelite - A type of sedimentary-rock rich in organic matter. Sapropelite and cannel-mudstone are both derived from the unlithified fine organic mud termed sapropel. These sapropels contain more inorganic matter and plant matter than the sapropels that form sapropelic coals. Inorganic sedimentary rocks rich in sapropel are classified according to their type of organic matter. Sapropelite is rich in alginite, whereas cannel-mudstone is rich in miospores. The total organic carbon content (TOC) can vary from less than 1% to as much as 81% in a sapropelite from Tasmania, although most sapropelites fall in the range of 8 to 55% TOC. In the Rock Classification Scheme, it is recommended that the lower limit for sapropelite should be 8% TOC and the upper limit 50% TOC. A sapropelite can be recognised in hand specimen by its bituminous smell and by the curled sliver of rock produced when it is scraped with a pen knife. Sapropelites can be subdivided into lamalginite and telaginite by reference to the properties of the organic matter. British Geological Survey Research Report RR/99/03, section 6.3, table 18 and fig. 10. Synonym: oil shale. | SAPEL |
| Saprolite - A type of regolith. It consists of highly to completely weathered materials derived from the in situ alteration and decomposition of parent rock mainly by chemical weathering processes, but which retain evidence of the original rock texture, fabric and structure. It may be classified as engineering soils falling into rock weathering grades IV (highly weathered) and V (completely weathered); that is, those weathering grades where more than 50% of the parent rock material is decomposed or disintegrated to soil. British Geological Survey Research Report RR/99/04, appendix 2. | SAPRO |
| Sandstone, conglomerate, siltstone and basalt lava | SCSBL |
| Shoshonite - A potassic basaltic-trachyandesite. British Geological Survey Research Report RR/99/06, section 5.2 and figs. 17b, 20. | SHOSH |
| Smectite-claystone - A type of monomineralic aluminium-silicate sedimentary rock in which the aluminium-silicate mineral is smectite. It is the lithified equivalent of smectite-clay. Bentonite and fullers earth may be considered synonyms for smectite-claystone. Bentonite is a soft, plastic, porous, light-coloured rock composed essentially of clay minerals from the smectite group plus colloidal silica, and produced by chemical alteration of volcanic ash. Fullers earth is a clay consisting largely of hydrated aluminium silicates (e.g. smectite), with a high proportion of water and little plasticity. It is formed by in-situ decomposition of igneous rocks containing a high proportion of glass. British Geological Survey Research Report RR/99/03, sections 9.1 and 13.6, and table 19. | SMCCST |
| Serpentinite, metabasalt, metalimestone and psammite | SMLP |
| Sylvite-stone - A type of non-carbonate salt that is composed of particles of the chloride mineral sylvite. British Geological Survey Research Report RR/99/03, section 7.1 and fig. 11. | SYLVST |
| Tuffaceous-mudstone with clasts of pillowed basalt and volcaniclastic rock | TMPBVR |
| Trachybasalt - A type of trachytic-rock, classified using the total alkali silica (TAS) classification. The TAS classification may be used if the mineral mode of a normal fine-grained crystalline rock cannot be determined due either to the presence of glass or to the fine-grained nature of the rock. The definition of trachybasalt is as shown in British Geological Survey Research Report RR/99/06, section 5.2 and figs. 17b, 20. | TRBA |
| Trachybasalt to trachyandesite | TRBAND |
| Trachybasalt and basalt | TRBB |
| Tuff, calcareous-basaltic | TUFCB |
| Tuff, volcaniclastic-igneous-rock and basaltic lava | TVSB |
| Ulexite-stone - A type of non-carbonate salt that is composed of particles of the borate mineral ulexite. British Geological Survey Research Report RR/99/03, section 7.1 and fig. 11. | ULEXST |
| Volcaniclastic-rock, hydrothermally-altered | VCRHA |
| Weathered rock - A type of regolith. It consists of weathered material which, depending on degree of disintegration, may be described in terms of rock material weathering grades II (slightly weathered), III (moderately weathered), IV (highly weathered), V (completely weathered), or VI (residual soil). In engineering geology terms, slightly to moderately weathered material falling into weathering grades II and III are considered as weathered rock for engineering purposes, and grades IV to VI as soil. Saprolite refers to soil-like grade IV and V material which has been altered and decomposed by chemical weathering processes. British Geological Survey Research Report RR/99/04, appendix 2. | WRC |