BGS Rock Classification Scheme
Chert - A type of siliceous rock. It usually has a porosity of less than 10%. Chert is dense, very hard, and has a vitreous lustre. It can be further classified as opaline-chert and quartzose-chert according to the type of silica. It may not be possible to accurately use this classification without X-ray analysis. In addition, the root names jasper, flint, and agate are available to describe distinctive types. British Geological Survey Research Report RR/99/03, section 8.2 and fig. 12.
| Code | CHRT |
|---|---|
| Description | Chert - A type of siliceous rock. It usually has a porosity of less than 10%. Chert is dense, very hard, and has a vitreous lustre. It can be further classified as opaline-chert and quartzose-chert according to the type of silica. It may not be possible to accurately use this classification without X-ray analysis. In addition, the root names jasper, flint, and agate are available to describe distinctive types. British Geological Survey Research Report RR/99/03, section 8.2 and fig. 12. |
| Qualifiers | No qualifiers currently exist. |
| Definition | Sedimentary rock with >50% silica of biogenic or chemical origin, porosity <10% hard, dense with vitreous lustre. Crystals generally <0. 004mm, cryptocrystalline. |
| Linked data | http://data.bgs.ac.uk/id/EarthMaterialClass/RockName/CHRT |
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.