Bog-oak, or abonos, is formed in a long process of fossilisation, whereby oak timber lies submerged in muddy and sandy soil. Over the course of hundreds (and sometimes thousands) of years the limited amounts of oxygen, along with the minerals and iron in the water, as well as other compounds from underground waters increase the level of tannin in the timber. This in turn causes the timber to acquire a much deeper and dark colour. The maturation process also strengthens the timber, which then has to undergo specialised treatment during processing. The extraction of bog-oak is in itself a very difficult process, and the number of locations where it can be obtained is limited.
All of these variables contribute to the unique quality both of the material and, consequently, the end product.