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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-life|half-lives]] for the decay of U₂₃₈ to Pb₂₀₆ or of U₂₃₅ to Pb₂₀₇. <ref>http://geology.about.com/od/geotime_dating/a/uraniumlead.htm</ref>

'''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-life|half-lives]] for the decay of U₂₃₈ to Pb₂₀₆ or of U₂₃₅ to Pb₂₀₇. <ref>http://geology.about.com/od/geotime_dating/a/uraniumlead.htm</ref>

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, the formation of the crystal is given a reliable date.  Zircon is also preferred for it high toughness and ease of separation from other rocks.

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, the age of the crystal can be determined.  Zircon is also preferred for its high toughness and ease of separation from other rocks.

Uranium-lead dating has been used to place dates on the end of the [[Permian|Permian period]] and the beginning of the [[Triassic|Triassic period]] with a margin of error much smaller than other dating methods had given.<ref>http://www.physorg.com/news1197.html</ref>

Uranium-lead dating has been used to place dates on the end of the [[Permian|Permian period]] and the beginning of the [[Triassic|Triassic period]] with a margin of error much smaller than other dating methods had given.<ref>http://www.physorg.com/news1197.html</ref>