Bøggildite. A new phosphate-fluoride from Ivigtut, South Greenland

Abstract

A new compound fluoride, phosphate-fluoride, was discovered by R. Bøgvad in 1950 in the boundary rock of the cryolite mass in the quarry in Ivigtut, South Greenland. He published a brief notice of the fact and had managed to give the mineral the name bøggildite in honour of Professor em. O. B. Bøggild, when Bøgvad died in the summer of 1952 in the midst of his work in Ivigtut. The folIowing description is made on the material found by Bøgvad. Further material has not been discovered, and there thus exists only a good 100 grams of the mineral. It is monoclinic, X-ray examinations showing that it is pseudorhombic, belonging to space group No. 14 P²1/c. It appears in columnar aggregates up to 12 mm long and some millimeters wide; it is salmon-coloured. Bøggildite is colourless under the microscope; α, β, γ are respectively 1.462, 1.466 and 1.469. 2 V lies between 78 and 80°. Axial dispersion can hardly be seen. The composition of the mineral corresponds to the formula Na₂Sr₂A₁₂(PO₄)F₉. It may be grouped together with the mineral known from Ivigtut, jarlite.