BGS Rock Classification Scheme

Exotic crystalline igneous rock - These are the chemically and/or mineralogically exotic crystalline igneous rocks. In the Rock Classification Scheme, this class includes carbonatite, melilitic rock, kalsilitic rock, kimberlite, lamproite, leucitic rock, and lamprophyre. Rocks in these groups have sufficiently unusual mineral and chemical compositions that they are not classified using the modal (QAPF and ultramafic diagrams) or chemical (e.g. TAS) methods by which normal crystalline igneous rocks are classified. Although they comprise only a tiny proportion of all crystalline igneous rocks, the unusual characteristics and distinctive field settings of the exotic igneous rocks means they have attracted a large amount of attention from geologists. British Geological Survey Research Report RR/99/06, section 1.3 and fig. 1.

Code ECR
Description Exotic crystalline igneous rock - These are the chemically and/or mineralogically exotic crystalline igneous rocks. In the Rock Classification Scheme, this class includes carbonatite, melilitic rock, kalsilitic rock, kimberlite, lamproite, leucitic rock, and lamprophyre. Rocks in these groups have sufficiently unusual mineral and chemical compositions that they are not classified using the modal (QAPF and ultramafic diagrams) or chemical (e.g. TAS) methods by which normal crystalline igneous rocks are classified. Although they comprise only a tiny proportion of all crystalline igneous rocks, the unusual characteristics and distinctive field settings of the exotic igneous rocks means they have attracted a large amount of attention from geologists. British Geological Survey Research Report RR/99/06, section 1.3 and fig. 1.
Qualifiers No qualifiers currently exist.
Definition Crystalline intrusive/extrusive rock, chemically & mineralogically exotic, crystal size not defined, includes very small volume of igneous rocks; carbonatites, melilitic, kalsilitic, leucitic rocks, kimberlites, lamproites, lamprophyres
Linked data http://data.bgs.ac.uk/id/EarthMaterialClass/RockName/ECR

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.