It arose from the fallen trees, which lay for hundreds of years under the surface of the water. Dark colour is formed as a result of reaction with water containing iron.
Black oak is found throughout almost Europe, but the largest of its clusters are located in the basins of the rivers of Central and Southern Europe. In Poland, the largest finds are found near Dębica and Szprotawa[2]. The largest exposed specimen of the black oak is located in the Museum of Agates and Petrified Trees in Dąbrowa Tarnowska and is 2 meters in diameter.
The estimated world deposits of black oak are smaller than the world's diamond deposits. In Tsarist Russia, the possession of black oak furniture was punishable by death, as it was reserved for the ruling family. Currently, Polish legislation stipulates that the deposits of black oak embedded in rivers and underground are owned by the State Treasury ąb"[1].