In a number of samples where the abundance of 204Pb was very low no attempt was made to measure the amount of it as the determination would be of no particular value. (Nier 1939, 156)Cook deduced that the lead-208 could not be "common" lead (that is, lead present at solidification of the ore) because common lead always includes lead-204. The lead-208 is certainly not derived from decay of thorium-232, because there is no trace of thorium-232 left in the sample. However, since the amount of lead-208 in the samples is small and we have no reason to believe that lead-204 is not present, the lead-208 is almost certainly common lead.