The Richardton meteorite, a 90-kilogram H5 ordinary chondrite, fell between Mott and Richardton in western North Dakota on June 30, 1918, and was directly witnessed, fixing its arrival in both time and place. Its fragments were later recovered across a strewn field about 9 miles by 5 miles, showing that it broke apart in the atmosphere before reaching the ground. Richardton became especially important to science in 1960, when John Reynolds identified excess xenon-129 in it, linking the meteorite to former iodine-129 in the solar nebula and making it important to early studies of Solar System chronology and chemical history.