BGS Rock Classification Scheme
Alkali-feldspar-granite - A type of granitic-rock. In the Rock Classification Scheme, it is a granitic rock in which plagioclase comprises less than 10% of the total feldspar. The mineral mode plots in field 2 of the quartz - alkali feldspar - plagioclase - feldspathoid (QAPF) diagram. British Geological Survey Research Report RR/99/06, section 5.1 and figs. 9, 11, 12.
| Code | AFGN |
|---|---|
| Description | Alkali-feldspar-granite - A type of granitic-rock. In the Rock Classification Scheme, it is a granitic rock in which plagioclase comprises less than 10% of the total feldspar. The mineral mode plots in field 2 of the quartz - alkali feldspar - plagioclase - feldspathoid (QAPF) diagram. British Geological Survey Research Report RR/99/06, section 5.1 and figs. 9, 11, 12. |
| Qualifiers | No qualifiers currently exist. |
| Definition | Coarse-grained, av. between 2-16mm normal crystalline intrusive rock; quartz 20-60% of QAPF, feldspar >90% alkali feldspar, +/-mica/amphibole |
| Linked data | http://data.bgs.ac.uk/id/EarthMaterialClass/RockName/AFGN |
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.