The following is a list of rock types recognized by petrologists.
There is no agreed number of specific types of rocks. Any unique
combination of chemical composition mineralogy grain size texture
or other distinguishing characteristics can describe rock types.
Additionally different classification systems exist for each major
type of rock.[citation needed] There are three major types of rock
sedimentary metamorphic and igneous. They are all identified by
their texture streak and location among other factors.