This type of classification requires a complete chemical analysis of the rock in order to pigeonhole a sample, and is not practical under field conditions where only a hand lens and hammer are available. A chemical classification system has been proposed for volcanic rocks and a comparable scheme for plutonic rocks is not available. This leaves us with a system based on mineralogy. The one gaining application is the result of several years work by the IUGS Subcommission on the Classification of Igneous Rocks or Streckeissen Classification. The system is simple to use, can be applied in the field, using a hand lens and a hammer.
Further subdivisions are dependant on the type and percentage of mafic minerals present.
Two systems have been proposed - Handouts.