Editing Radiometric dating (section)

===Luminescence dating methods===
{{Main|Luminescence dating}}

Luminescence dating methods are not radiometric dating methods in that they do not rely on abundances of isotopes to calculate age. Instead, they are a consequence of [[background radiation]] on certain minerals. Over time, [[ionizing radiation]] is absorbed by mineral grains in sediments and archaeological materials such as [[quartz]] and [[potassium feldspar]]. The radiation causes charge to remain within the grains in structurally unstable "electron traps". Exposure to sunlight or heat releases these charges, effectively "bleaching" the sample and resetting the clock to zero. The trapped charge accumulates over time at a rate determined by the amount of background radiation at the location where the sample was buried. Stimulating these mineral grains using either light ([[optically stimulated luminescence]] or infrared stimulated luminescence dating) or heat ([[thermoluminescence dating]]) causes a luminescence signal to be emitted as the stored unstable electron energy is released, the intensity of which varies depending on the amount of radiation absorbed during burial and specific properties of the mineral.<ref>{{Cite journal |last1=Roberts |first1=Richard G. |last2=Jacobs |first2=Zenobia |last3=Li |first3=Bo |last4=Jankowski |first4=Nathan R. |last5=Cunningham |first5=Alastair C. |last6=Rosenfeld |first6=Anatoly B. |date=2015-04-01 |title=Optical dating in archaeology: thirty years in retrospect and grand challenges for the future |url=https://linkinghub.elsevier.com/retrieve/pii/S0305440315000667 |journal=Journal of Archaeological Science |series=Scoping the Future of Archaeological Science: Papers in Honour of Richard Klein |volume=56 |pages=41–60 |doi=10.1016/j.jas.2015.02.028 |bibcode=2015JArSc..56...41R |issn=0305-4403}}</ref>

These methods can be used to date the age of a sediment layer, as layers deposited on top would prevent the grains from being "bleached" and reset by sunlight. Pottery shards can be dated to the last time they experienced significant heat, generally when they were fired in a kiln.<ref>{{Cite journal |last1=Roberts |first1=Richard G. |last2=Jacobs |first2=Zenobia |last3=Li |first3=Bo |last4=Jankowski |first4=Nathan R. |last5=Cunningham |first5=Alastair C. |last6=Rosenfeld |first6=Anatoly B. |date=2015-04-01 |title=Optical dating in archaeology: thirty years in retrospect and grand challenges for the future |url=https://linkinghub.elsevier.com/retrieve/pii/S0305440315000667 |journal=Journal of Archaeological Science |series=Scoping the Future of Archaeological Science: Papers in Honour of Richard Klein |volume=56 |pages=41–60 |doi=10.1016/j.jas.2015.02.028 |bibcode=2015JArSc..56...41R |issn=0305-4403}}</ref>