The sulfate fluorides are double salts that contain both sulfate and fluoride anions.
They are in the class of mixed anion compounds.
Fluoride sulfates were first discovered by Jean Charles de Marignac in 1859.
[1][2] Some elements such as cobalt or uranium can form complexes that contain fluoride and sulfate groups, and would be referred to as fluoro and sulfato metallates.
2V: measured: 30° , calculated: 40° Max birefringence: δ = 0.009 Max birefringence: δ = 0.024 2V: Measured: 23° Max Birefringence: δ = 0.025 Max birefringence: δ = 0.008 2V: measured: 68° calculated: 84° Max birefringence δ = 0.047 colourless Max Birefringence: δ = 0.003 Max birefringence: δ = 0.008 Max Birefringence:δ = 0.018 Max Birefringence δ = 0.024 Max birefringence: δ = 0.017 Max birefringence: δ = 0.005 Max Birefringence: δ = 0.002 Max birefringence:δ = 0.005 Biaxial (-) nα = 1.477(2) nβ = 1.485(2) nγ = 1.489(2) 2V: measured: 70° calculated: 70.2° Max birefringence: δ = 0.012 2V: calculated: 56° Max birefringence: δ = 0.021 2V: measured: 48° , calculated: 44° Max birefringence: δ = 0.014 Max birefringence: δ = 0.008