BGS Rock Classification Scheme
Rock, charnockitic - A type of coarse-grained normal crystalline rock. The charnockitic suite of rocks is usually characterised by the presence of orthopyroxene (or fayalite plus quartz, though in such assemblages fayalite is invariably altered) and, in many such rocks, perthite, mesoperthite or antiperthite. Primary hydrous minerals are generally absent. They are commonly associated with norites and anorthosites and are linked closely with high-grade metamorphic terrains. Despite being composed largely of feldspar and quartz, charnockitic rocks are generally melanocratic due to very dark feldspar crystals, which also have a characteristically greasy appearance. British Geological Survey Research Report RR/99/06, section 5.1. Examples (root name and qualifier): charnockitic granite, charnockitic monzonite, charnockitic tonalite.
| Code | CHARNR |
|---|---|
| Description | Rock, charnockitic - A type of coarse-grained normal crystalline rock. The charnockitic suite of rocks is usually characterised by the presence of orthopyroxene (or fayalite plus quartz, though in such assemblages fayalite is invariably altered) and, in many such rocks, perthite, mesoperthite or antiperthite. Primary hydrous minerals are generally absent. They are commonly associated with norites and anorthosites and are linked closely with high-grade metamorphic terrains. Despite being composed largely of feldspar and quartz, charnockitic rocks are generally melanocratic due to very dark feldspar crystals, which also have a characteristically greasy appearance. British Geological Survey Research Report RR/99/06, section 5.1. Examples (root name and qualifier): charnockitic granite, charnockitic monzonite, charnockitic tonalite. |
| Qualifiers | charnockitic |
| Definition | Coarse-grained, av. between 2-16mm normal crystalline intrusive rock with perthitic feldspars (usually dark coloured), magnetite & pyroxene (usually orthopyroxene, commonly hypersthene or altered fayalite & quartz) |
| Linked data | http://data.bgs.ac.uk/id/EarthMaterialClass/RockName/CHARNR |
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.