No, slate is not an igneous rock. It is classified as a metamorphic rock. Slate forms from the transformation of shale, which is a sedimentary rock, under conditions of high pressure and temperature.
The metamorphic process causes the clay particles in shale to recrystallize, forming a fine-grained rock with a distinct foliation. This foliation allows slate to break easily into flat sheets, making it a popular material for roofing and flooring.
In contrast, igneous rocks are formed from the cooling and solidification of molten rock, either magma or lava. Some common examples of igneous rocks are granite and basalt. Therefore, while slate has unique properties and uses, its origins and formation process place it firmly in the category of metamorphic rocks, not igneous.