The three main groups are igneous rock, sedimentary rock and metamorphic rock. How do igneous rocks form? Igneous rock forms when magma or lava cools and hardens. Gneiss is a kind of rock that forms when heat and pressure inside Earth change granite. To what group of rocks does gneiss belong? read more
Sandstone belongs to the sedimentary rock group. This is a group ofrocks that are created through the compression of sediments over aperiod of time. read more
A Gneiss rock is a rock that is gray to white in color and is usually coarse textured with parallel bands of minerals. read more