Bog oak (the name derives from French – marrais meaning a bog) ordinary called black represents oak wood mineralized with metal salts in natural conditions. Owing to riverside erosion and changes of river-beds all riverside oak-woods were buried under the water for thousand years. Oak changed its chemical composition under the influence of tannin (halotannic acid).
As a result bog oak has gained unique physical properties: strength, durability and unique color spectrum. As long as all oak trunks were under the different conditions every single log gained its own unique structure and color. According to the quantity of salt in metals (mostly iron) contained in the river water and tannin contained in the wood, the color changed its tone - from white-pink to black.
Tone and coloring power depended on natural conditions and mineralization period. To gain black color the oak needs the fuming period from 1000 up to 2000 years. Formation of the oak deposit happen owing to some necessary conditions: oak-woods on the river banks, speed of the river current favourable for the process of mineralization, saturation of water with mineral salts, certain structure of the river fluvial sediments and time factor. It follows from this that bog oak is really unique material because the probability of coincidence of the above-listed factors is rather low.