Carbon dating leather
In principle, any material of plant or animal origin, including textiles, wood, bones and leather, can be dated by its content of carbon 14, a radioactive form of carbon in the environment that is incorporated by all living things.
The best gauge they have found is dendrochronology: the measurement of age by tree rings.
Accurate tree ring records of age are available for a period extending 9,000 years into the past.
Uranium 234, a radioactive element present in the environment, slowly decays to form thorium 230.
Using a mass spectrometer, an instrument that accelerates streams of atoms and uses magnets to sort them out according to mass and electric charge, the group has learned to measure the ratio of uranium to thorium very precisely.
They arrived at this conclusion by comparing age estimates obtained using two different methods - analysis of radioactive carbon in a sample and determination of the ratio of uranium to thorium in the sample.