Using isotope dilution the ages of fourteen lepidolite hand samples representing eight different areas have been determined. Lepidolites from Pope’s Claim, Southern Rhodesia, Bikita, Southern Rhodesia and Alto Ligonha, Portuguese East Africa, were investigated in a series of statistical experiments and the ages and 95% confidence limits for the mean of the determinations are: Pope’s Claim '
A
' 2931 ± 63 million years, Pope’s Claim '
B
' 2955 ± 75 million years; Bikita '
A
' 2978 ± 43 million years, Bikita '
B
' 2961 ± 25 million years; Alto Ligonha '
A
' 533 ± 8·3 million years, Alto Ligonha '
B
' 528 ± 8·5 million years. Ḟurther samples from Bikita show ages ranging from 2830 to 3040 million years and all lying within the 95% confidence limit for a single determination. The Karibib area, South-West Africa, is dated from three separate samples as 600 ± 70 million years. The other ages determined are Hombola, Tanganyika (2990 ± 200 million years), Antelope Mine, Southern Rhodesia (2675 ± 150 million years), Tsarafara, Madagascar (652 ± 45 million years) and Mica Siding North-East Transvaal (2040 ± 150 million years). In these cases the uncertainty quoted covers the range of the determinations made. The relationship of these ages to ages determined using
87
Rb—
87
Sr decay elsewhere and to U—Pb ages for the same areas is discussed, and it is shown that for the Rhodesian shield a value of
λ
= 1·26 ± 0·04 x 10
-11
for
87
Rb decay would lead to agreement with the U-Pb ages.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.