How many types of rock do we have?

Answer 1

There are two classifications of igneous rocks: extrusive, those formed on the surface, and intrusive, those formed underground. The most common igneous rock is basalt, followed by granite. Types of variations of these two alone are very high in number.

Answer 2

There are thousands, depending upon how you classify them.

The simplest division is Igneous/Plutonic, Sedimentary, and Metamorphic.

Beyond this you may classify them as carbonates, sulphates and so on.

Answer 3

The three main types of rock , are Igneous, Metamorphic and Sedimentary.

Igneous is formed by heat and pressure from volcanic eruptions.

Metamorphic is sedimentary rock that has been subject to heat and pressure.

Sedimentary is rock/sand granules laid down by river and sea and compressed together by the overlying weight.