section_path: Age/Radiocarbon dating
section_name: Radiocarbon dating
paragraph_text: Radiocarbon dating
  
  Mortar was used generously in the Great Pyramid's construction. In the mixing process ashes from fires were added to the mortar, organic material that could be extracted and radiocarbon dated. A total of 46 samples of the mortar were taken in 1984 and 1995, making sure they were clearly inherent to the original structure and could not have been incorporated at a later date. The results were calibrated to 2871–2604 BC. The old wood problem is thought to be mainly responsible for the 100–300 year offset, since the age of the organic material was determined, not when it was last used. A reanalysis of the data gave a completion date for the pyramid between 2620 and 2484 BC, based on the younger samples.
  
  In 1872 Waynman Dixon opened the lower pair of "Air-Shafts", previously closed at both ends, by chiseling holes into the walls of the Queen's Chamber. One of the objects found within was a cedar plank, which came into possession of James Grant, a friend of Dixon. After inheritance it was donated to the Museum of Aberdeen in 1946; however, it had broken into pieces and was filed incorrectly. Lost in the vast museum collection, it was only rediscovered in 2020, when it was radiocarbon dated to 3341–3094 BC. Being over 500 years older than Khufu's chronological age, Abeer Eladany suggests that the wood originated from the center of a long-lived tree or had been recycled for many years prior to being deposited in the pyramid.