Of the three basic rock types, igneous rocks are most suited for radiometric dating. Metamorphic rocks may also be radiometrically dated. However, radiometric dating generally yields the age of metamorphism, not the age of the original rock.

What rocks Cannot be dated radiometrically?

Thus, sedimentary and metamorphic rocks can't be radiometrically dated. Although only igneous rocks can be radiometrically dated, ages of other rock types can be constrained by the ages of igneous rocks with which they are interbedded.

Why can't you radiometrically date sedimentary rocks?

Sedimentary rocks may have radioactive elements in them, but they have been re-worked from other rocks, so essentially, there radiometric clock has not been re-set back to zero.