Isotope persisted down to the present because their rate of decay is so slow (e.g. uranium-238 and potassium-40). Post-primordial isotopes were created by cosmic ray bombardment as cosmogenic nuclides (e.g., tritium, carbon-14), or by the decay of a radioactive primordial isotope to a radioactive radiogenic nuclide daughter (e.g. uranium to radium). A few isotopes are naturally synthesized as nucleogenic nuclides, by some other natural nuclear reaction, such as when neutrons from natural nuclear fission are absorbed by another atom. As discussed above, only 80 elements have any stable isotopes, and 26 of these have only one stable isotope. Thus, about two-thirds
Ixcateopan (archaeological site) de productos derivados del algodón, materia prima que debió ser la principal fuente de abasto y de culto en la región. The archaeological zone consists of a series of overlays built on a natural elevation of the terrain, which occupies approximately 5 thousand square meters. Construction materials employed include: stone slabs, marble, limestone, boulders; and stucco and red paint used for finishing. Ceramic artifacts are a large and important group of samples found, generally mentioned in archaeological reports, serve to describe as well as chronological placement of sites, although seldom are investigation and study specific subjects The typical ceramics used