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Potassium-argon determinations on some London medieval honestones
D D B Crosby and J G Mitchell
In a survey of the provenance of medieval British metamorphic honestones, conventional potassium-argon whole-rock isotopic ages were measured on fifteen specimens from London sites ranging in date from the mid 12th to the mid 15th century.
Two principal types of metamorphic honestone were used in Britain during this period: Norwegian Ragstone, from the Eidsborg quarries of southern Norway, and Purple Phyllite, probably also from central-southern Norway. The London sample contained no instances of Purple Phyllite. There were twelve instances of Norwegian Ragstone; three of these returned ages significantly lower than would have been expected, and possible explanations for this are advanced.
[Transactions 38 (1987), pp 159 – 64; abstract by Francis Grew, 21-Oct-1997]
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