Scientists date igneous rock using elements that are slow to decay, such as uranium and potassium. By dating these surrounding layers, they can figure out the youngest and oldest that the fossil might be; this is known as bracketing the age of the sedimentary layer in which the fossils occur.

Why are igneous rocks the best type of rock sample for radiometric dating?

The Most Useful Rock Samples Igneous rocks are the best types of rock samples to use for radiometric dating. When igneous rock forms, elements are separated into different minerals in the rock. Thus, when they form, minerals in igneous rocks often contain only a parent isotope and none of the daughter isotope.

Is absolute dating used for igneous rocks?

Potassium-Argon Dating Measuring the ratio of potassium-40 to argon-40 will yield a good estimate of the age of the sample. Potassium is a common element found in many minerals such as feldspar, mica, and amphibole. The technique can be used to date igneous rocks from 100,000 years to over a billion years old.

How is the absolute age of an igneous rock determined?

Relative age is the age of a rock layer (or the fossils it contains) compared to other layers. It can be determined by looking at the position of rock layers. Absolute age is the numeric age of a layer of rocks or fossils. Absolute age can be determined by using radiometric dating.