Fluorine is an element that is found in most ground water around the world. It can be used as a relative dating technique.

Skeletal remains buried in the earth are subject to a wide range of chemical changes. One of these changes can occur when percolating ground water comes into contact with the remains. The ground water inundates the bone remains with a solution of minerals drawn from local soils. This can cause a change in the mineral composition of the bone. Hydroxyl ions are displaced with a form of soluble fluorides. These ions form fluorapatite which is markedly less soluble. Over time, more and more fluorides are accumulated. The rate varies depending on the specific condition in the soil of the area and increases with age.

Fluorine dating is chiefly of value in determining whether bone implements or human skeletal remains found in association with other bones were buried at the same time. It was fluorine dating that was instrumental in the debunking of Piltdown Man. The Piltdown controversy lasted until 1949 when the Piltdown skull and jawbone were subjected to fluorine testing. The levels of fluorine in the skull and jawbone were significantly lower then in other bone specimens collected from the same area. After further testing the jawbone and a canine tooth proved to contain no more fluorine than fresh bones and teeth. The skull contained enough fluorine to indicate that it was not modern.

Citations

Michels, Joseph W., Pennsylvania State University (1973) Dating Methods in Archaeology

Hester, Heizer and Graham, Mayfield Publishing Company (1975) Methods in Archaeology