By measuring the C concentration or residual radioactivity of a sample whose age is not known, it is possible to obtain the number of decay events per gram of Carbon.
By comparing this with modern levels of activity (1890 wood corrected for decay to 1950 AD) and using the measured half-life it becomes possible to calculate a date for the death of the sample. As a result of atomic bomb usage, C ages of objects younger than 1950.
Willard Libby and his colleague Ernest Anderson showed that collected from sewage works had measurable radiocarbon activity whereas methane produced from petroleum did not.
Perseverance over three years of secret research to develop the radiocarbon method came into fruition and in 1960 Libby received the Nobel Prize for chemistry for turning his vision into an invaluable tool.
At about 50 000 to 60 000 years, the limit of the technique is reached (beyond this time, other radiometric techniques must be used for dating).
If the rock containing these minerals is heated, the tracks will begin to disappear.