An example of a rock formed by wood subjected to pressure and heat is

The rock that is formed by wood subjected to pressure and heat is called "lignite". Lignite is a type of coal that is considered the lowest rank of coal due to its relatively low heat content and carbon content. Lignite is formed from partially decomposed plant material that has been subjected to increasing amounts of pressure and heat over time. As the plant material becomes buried and compressed, it eventually transforms into lignite through a process called coalification. Therefore, lignite is a sedimentary rock that is formed from the compressed and heated remains of plants, including wood. It is typically brownish-black in color and has a relatively low density compared to other types of coal.