A technique used in the analysis of artifact composition, particularly iron-bearing minerals in pottery. It involves the measurement of the gamma radiation absorbed by the iron nuclei, which provides information on the particular iron compounds in the sample, and hence on the conditions of firing when the pottery was being made. Samples are bombarded with gamma rays and a record made of the detected amount of absorption by iron nuclei. The use of this method of physical analysis has been confined mainly to the examination of iron compounds, though other uses have been suggested. The Mössbauer effect of recoil-free emission and absorption of gamma rays only occurs with a limited number of isotopes, of which one of the iron isotopes is useful in archaeological contexts. Because of its sensitivity to short-range crystalline order, the technique is better for examining poorly crystallized iron-bearing minerals than X-ray diffraction. This type of spectroscopy is also used for the study of nuclear hyperfine structure, chemical shifts, and chemical analysis.