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Geochemical Journal
Geochemical Journal An open access journal for geochemistry
Published for geochemistry community from Geochemical Society of Japan.

Magnetic separation of calcite and aragonite for use in radioactive carbon analysis

Geochemical Journal, Vol. 48, No. 2, P. 113-119, 2014


Aragonite and calcite often coexist; as such, separating these very similar minerals is an important step in undertaking research on these two phases individually. One approach to discriminating between the two phases is to stain a sample using Meigen’s solution, which is a solution of cobalt nitrate, a magnetic substance: aragonite is stained purple while calcite is still white. Magnetic separator can also be employed, and this instrument has been used in a number of environmental and industrial applications. Here, we integrate the use of the magnetic characteristics of Meigen’s solution with magnetic separation to provide an enhanced method of aragonite and calcite separation semi-automatically instead of manually as done in the past. Imperfect staining and/or the aggregation of differing minerals means that, a 250–125 μm is optimal grain size for aragonite separation that is treated at 70 deg.C - 15 minutes treatment as well as of calcite separation that is treated at 80–90 deg.C - 10 minutes treatment. The effectiveness of this approach is demonstrated by defining a radioactive carbon profile of carbonate samples collected from a chimney from Conical Seamount, in the Mariana forearc.


magnetic separation, aragonite, calcite, cobalt, Meigen’s solution, peak intensity

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