There are three kinds of rock: igneous, sedimentary, and metamorphic.

Are there 4000 types of rocks?

Some rocks are made of a single type of mineral. But most are made of a few types joined together. Altogether there are about 4,000 types of minerals. Every mineral has its own chemical composition and properties, such as what temperature it melts at, how hard it is, what color it is, and how lustrous (shiny) it is.

Is there a 4th type of rock?

Rock can also form in the absence of a substantial pressure gradient as material that condensed from a protoplanetary disk, without ever undergoing any transformations in the interior of a large object such as a planet or moon. Astrophysicists classify this as a fourth type of rock: primitive rock.