Absolute Isotopic Abundance of Terrestrial Silver

Isotopic abundance ratios are reported for a commercial silver nitrate, 13 samples of native silver, and 11 silver minerals of various compositions and from widely distributed deposits. Collateral measurements of known mixtures of nearly pure silver isotopes permit the determination of absolute abundance ratios. Native silver from Cobalt, Ontario, previously reported as exhibiting statistically significant variation, is re-examined. Additional measurements are reported for samples from the same nugget and from the same region. Except for the original observation, no significant variation from normal abundance is observed for any of the samples. The Ag(107)/Ag(109) ratio obtained from pooling the data is 1.07597 with a 95 percent confidence limit of ±0.00055 for the effect of random errors and a total uncertainty of ±0.00135 when an allowance for the possible effects of known sources of systematic error is included.