An igneous rock is formed from the cooling and solidification of molten magma or lava. Option 1, Granite, is an example of an igneous rock. It is formed by the slow cooling and crystallization of magma deep underground. Option 3, Pumice, is also an igneous rock. It is formed from the rapid cooling of lava, which traps gas bubbles, giving it a porous texture. Option 4, Basalt, is another igneous rock. It is formed from the rapid cooling of lava on the Earth`s surface.

Option 2, Gneiss, is the correct answer as it is not an igneous rock. Gneiss is a metamorphic rock, which means it has undergone significant changes in temperature and pressure. It is formed from the recrystallization of existing rocks, such as granite, through the process of metamorphism. Gneiss typically has a banded appearance due to the alignment of minerals during metamorphism.

Therefore, while options 1, 3, and 4 are all examples of igneous rocks, option 2, Gneiss, is not. It is a metamorphic rock.