Each of them typically exists in igneous rock, or rock made from cooled magma.
Fossils, however, form in sedimentary rock -- sediment quickly covers a dinosaur's body, and the sediment and the bones gradually turn into rock.
You can learn more about fossils, dinosaurs, radiometric dating and related topics by reading through the links on the next page.
Radiometric dating isn't the only method of determining the age of rocks.
Among these metamorphosed volcanic strata are amphibolites, belonging to the Brahma Schist.
These were originally basalt lava flows several meters to tens of meters thick.
Other techniques include analyzing amino acids and measuring changes in an object's magnetic field.
Scientists have also made improvements to the standard radiometric measurements.Dinosaur bones, on the other hand, are millions of years old -- some fossils are billions of years old.To determine the ages of these specimens, scientists need an isotope with a very long half-life.But this sediment doesn't typically include the necessary isotopes in measurable amounts.Fossils can't form in the igneous rock that usually does contain the isotopes.All 27 samples were sent to two well-credentialed internationally-recognized, commercial laboratories for radioisotope analyses—potassium-argon (K-Ar) at a Canadian laboratory, and rubidium-strontium (Rb-Sr), samarium-neodymium (Sm-Nd), and lead-lead (Pb-Pb), at an Australian laboratory.