Subfossil wood or abonos is wood that has lain for hundreds or thousands of years at the bottom of a swamp, river, lake or sea under deposits of gravel, mud and silt in anoxic conditions. The characteristic black color of abonos comes from the chemical reaction of tannins from the wood and iron from the water. Subfossil wood has changed physical and mechanical properties, due to the specific conditions in which it was formed. Recent and subfossil wood differ in composition, because the content of extractive substances and phenolic compounds in subfossil wood has decreased over the years, and the proportion of carbohydrates has also decreased. By comparing the content of inorganic elements in subfossil and recent wood of the same species, it was proven that subfossil wood has a higher total content of iron, calcium and magnesium, while recent wood has a higher total content of potassium. The cellulose content in subfossil wood is lower than in recent wood, while the lignin content is much higher in subfossil wood. The densities of recent and subfossil oak are similar, but it has been shown that increasing the age of abonos leads to an increase in its density. Subfossil wood has a wide range of uses, it can be used to make unique expensive decorations, furniture or musical instruments.