Which one of the following is not an igneous rock?

Which one of the following is not an igneous rock?

Granite
Gneiss
Pumice
Basalt
This question was previously asked in
UPSC CAPF – 2018
Igneous rocks are formed through the cooling and solidification of molten rock (magma or lava). Granite, pumice, and basalt are all types of igneous rocks: Granite is an intrusive igneous rock formed from slow cooling magma; Basalt is an extrusive igneous rock formed from rapidly cooling lava; Pumice is a highly porous extrusive igneous rock (volcanic glass). Gneiss, however, is a metamorphic rock formed from pre-existing rocks (like granite, shale, or volcanic rocks) that have been subjected to high temperature and pressure, resulting in recrystallization and often a banded appearance (foliation).
Igneous rocks form from molten rock. Metamorphic rocks form from pre-existing rocks altered by heat and pressure.
The three main rock types are igneous, sedimentary, and metamorphic. Igneous rocks are classified based on their composition and texture (which depends on cooling rate). Gneiss is a common high-grade metamorphic rock.