The London Hammer is an object of mysterious origin that has been the subject of much debate and speculation. It is a hammer made of iron and wood, found in a limestone rock formation near London, Texas in 1936. The hammer has been dated to the late Jurassic period, approximately 140 million
From Wikipedia
The London Hammer is a hammer made of iron and wood that was found in London, Texas in 1936. Part of the hammer is embedded in a limey rock concretion, leading some to regard it as an anomalous artifact. The tool is identical to late 19th-century mining hammers; one theory for its encasement in rock is that a deposit of highly soluble travertine may have formed and hardened around it within a relatively short time.