<P> 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 . There are three major types of rock, sedimentary, metamorphic, and igneous . They are all identified by their texture, streak, and location, among other factors . </P> <Dl> <Dd> Adakite - a class of intermediate to felsic rocks containing low amounts of yttrium and ytterbium </Dd> </Dl>

How many types of rock are there on earth
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