pretty people international dating service - Radiometric dating how stuff works
The decay constants for most of these systems have been confirmed in other ways, adding strength to our argument for the age of the earth., so there is one zirconium (Zi) for one silicon (Si) for four oxygen (O).One of the elements that can stand in chemically for zircon is uranium.This is why crystals are good for radiometric dating: the atoms in a crystal are extremely efficiently packed, and it's very difficult to get anything into a crystal such as a contaminant by any means short of destroying the crystal and re-growing it anew.
Obviously, if the substance you are measuring is contaminated, then all you know is the age since contamination, or worse, you don't know anything, because the contamination might be in the opposite direction - suppose, for example, you're looking at radio carbon (carbon 14, which is produced in the atmosphere by cosmic rays, and which decays into nitrogen).
Since you are exposed to the atmosphere and contain carbon, if you get oils from your skin onto an archeological artifact, then attempting to date it using radio carbon will fail because you are measuring the age of the oils on your skin, not the age of the artifact.
We call the original, unstable isotope (Uranium) the "parent", and the product of decay (Lead) the "daughter".
From careful physics and chemistry experiments, we know that parents turn into daughters at a very consistent, predictable rate.
For example, a problem I have worked on involving the eruption of a volcano at what is now Naples, Italy, occurred 38500 years ago with a plus or minus of 300 years.