Francolite is a carbonate rich variety of the mineral fluorapatite and is present in most sedimentary phosphorites. It has a variable chemical composition which can be represented by .R. A. Benmore, M. L. Coleman, and J. M. McArthur, Origin of is sedimentary francolite from its sulphur and carbon isotope composition. Nature 302: 516, 1983 The mineral was named after its occurrence at Wheal Franco, Whitchurch, Tavistock District, Devon, England.
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