Home >> Science & Nature >> Rocks & Minerals

How to Use Analytical Chemistry to Determine the Age of Rocks

The discovery of radioactivity in the 19th century brought with it many advances in science, from nuclear power to nuclear medicine. Scientists discovered that radioisotopes decayed at a specific rate measurable by analytical chemistry. Prehistoric animals absorbed these isotopes while living and they remained in the animals' fossils and surrounding rock. By analyzing rocks with specific isotopes, scientists can determine their exact ages by seeing how much the isotope has degraded. This is called radiometric dating and is one of the most accurate methods of age determination.

Things You'll Need

Magnetic separator
Acid
Dehydrator
Mass spectrometer

Instructions

- 1
  Dig up a rock or fossil which has not been weathered by time and climate. Examine the stratification of the surrounding rock to determine roughly the era the rock was located in, based on the layers above and below where the rock or fossil was found. This provides an estimated date to compare against the results of the radiometric dating.
- 2
  Determine the radioactive isotope you want to use for the dating process. There are many elements used for dating including carbon, strontium, rubidium and uranium. Crush the rock into small pieces. Place the pieces in a magnetic separator to separate the radioisotope from the other minerals in the rock.
- 3
  Dissolve the pieces of rock which include the radioisotope in acid. This will eliminate the rock, leaving only a concentration of radioisotopes. The type of acid or acids used depends on the type of rock and isotopes present. Dry the solution into a salt compound of concentrated radioisotopes using a dehydrator.
- 4
  Place the compound into a mass spectrometer. Analyze the compound. Create a diagram of the radioactive decay curve. Examine the diagram and calculate the age of the rock by looking at the decay curve. Rubidium-strontium dating provides results in millions of years.

Rocks & Minerals