BGS Rock Classification Scheme
Paraschist - A type of metasedimentary rock based on textural attributes. In the Rock Classification Scheme, it is defined as a medium-grained strongly foliated rock that can be readily split into flakes or slabs due to the well-developed preferred orientation of the majority of the minerals present, particularly those of platy or prismatic habit. Schists occur characteristically in areas of medium-grade metamorphism and can encompass a wide range of lithologies. Note the para- prefix indicates a rock that is thought to have a sedimentary protolith, in contrast with orthoschist which has an igneous protolith, and schist where the nature of the protolith is not defined. British Geological Survey Research Report RR/99/02, section 3.3.
| Code | PSCH |
|---|---|
| Description | Paraschist - A type of metasedimentary rock based on textural attributes. In the Rock Classification Scheme, it is defined as a medium-grained strongly foliated rock that can be readily split into flakes or slabs due to the well-developed preferred orientation of the majority of the minerals present, particularly those of platy or prismatic habit. Schists occur characteristically in areas of medium-grade metamorphism and can encompass a wide range of lithologies. Note the para- prefix indicates a rock that is thought to have a sedimentary protolith, in contrast with orthoschist which has an igneous protolith, and schist where the nature of the protolith is not defined. British Geological Survey Research Report RR/99/02, section 3.3. |
| Qualifiers | No qualifiers currently exist. |
| Definition | Medium-grained (av. 0.25-2mm) strongly foliated meta-sedimentary rock; (protolith undefined) splits into < 5mm slabs/flakes defined by well-developed planar orientation of platy/prismatic minerals |
| Linked data | http://data.bgs.ac.uk/id/EarthMaterialClass/RockName/PSCH |
CAVEAT
"Thumbnail" definitions attached to some of the table entries are an interim attempt to provide simple short descriptions of the "unqualified" rock types presented within the BGS Rock Classification Scheme. Every effort has been made to ensure accuracy and consistency but minor contradictions or omissions might be present. The BGS welcomes any feedback pointing out such minor imperfections and/or providing constructive comment and suggestions for improvement of the definitions. In the first instance such feedback should be directed to Dr Tim McCormick.