To establish the age of a rock or a fossil, researchers use some type of clock to determine the date it was formed. Geologists commonly use radiometric dating methods, based on the natural radioactive decay of certain elements such as potassium and carbon, as reliable clocks to date ancient events.
One of the most widely used and well-known absolute dating techniques is carbon-14 (or radiocarbon) dating, which is used to date organic remains. This is a radiometric technique, since it is based on radioactive decay.
What is the best rock for radiometric dating Why?
When you radiometrically date a mineral grain you are determining when it crystallized. Thus, you would like to use rocks whose crystals are roughly the same age. The easiest are igneous rocks in which all crystals are roughly the same age, having solidified at about the same time.