Borate sulfates are mixed anion compounds containing separate borate and sulfate anions.
They are distinct from the borosulfates where the borate is linked to a sulfate via a common oxygen atom.
Max birefringence δ = 0.024 β = 93.33° Z=4 2V 63° to 77° Max birefringence δ = 0.025 Max birefringence δ = 0.017 Max birefringence δ = 0.008 Uniaxial (+) nω = 1.475 nε = 1.496 Max birefringence δ = 0.021 Uniaxial (+/-) nω = 1.499 - 1.500 nε = 1.497 - 1.505 Max birefringence δ = 0.002 Max birefringence δ = 0.009