Francolite

Francolite is a carbonate rich variety of the mineral fluorapatite^[1] and is present in most sedimentary phosphorites. It has a variable chemical composition which can be represented by (Ca,Mg,Sr,Na)₁₀(PO₄,SO₄,CO₃)₆F₂₋₃.^[2] The mineral was named after its occurrence at Wheal Franco, Whitchurch, Tavistock District, Devon, England.^[1]

Francolite
Francolite found in Russia
General
Category	Phosphate minerals
Formula	(Ca,Mg,Sr,Na)10(PO4,SO4,CO3)6F2−3