What isotope is appropriate for dating rocks that are billions of years old?

Uranium-lead (U-Pb) dating is an appropriate method for dating rocks that are billions of years old. This technique relies on the decay of uranium isotopes (U-238 and U-235) into stable lead isotopes (Pb-206 and Pb-207). It is particularly effective for dating zircon crystals found in igneous rocks, which can survive geological processes and retain the isotopic ratiOS needed for accurate age determination. U-Pb dating can provide ages for rocks ranging from millions to over four billion years.