Uranium-lead dating
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Uranium-lead dating is one of several radiometric dating techniques. It is the oldest method and generally considered to be the most accurate. It dates a material based on the half-lives for the decay of U238 to Pb206 or of U235 to Pb207. [1]
This dating method is used on several minerals, however, it works best with the mineral zircon (ZrSiO4). Because the formation of zircon rejects lead from its structure but allows uranium in the place of zirconium atoms, any lead present in it's structure must be radiogenic. Given the amount of radiogenic lead and uranium in a sample, the age of the crystal can be determined. Zircon is also preferred for its high toughness and ease of separation from other rocks.