A SEARCH FOR SUPERHEAVY ELEMENTS IN NATURE

The results of a search for elements 109 and 110 in nature are reported. No significant activity was observed in the sample by solid track measurements, but an excess a-activity exists in the 4.3-4.6 MeV region as shown by the a-pulse-height spectrum of the nickel anode mud sample. Assuming a half life of 108 years for the superheavy elements concerned, the upper limits of the concentration of elements 109 and 110 are estimated at 10-13 and 10-11 grams per gram of sample respectively.