Sulfate carbonate

Sulfate carbonate minerals are in the 7.DG and 5.BF Nickel-Strunz groupings.

[1] They may be formed by crystallization from a water solution, or by melting a carbonate and sulfate together.

[2] Silvialite can substitute about half its sulfate with carbonate[3] and the high temperature hexagonal form of sodium sulfate (I) Na2SO4 can substitute unlimited proportions of carbonate instead of sulfate.

2V: measured: 34° , calculated: 32° Max birefringence: δ = 0.045 2V: measured: 85° , calculated: 84° Max birefringence: δ = 0.091 bluish green Max birefringence: δ = 0.030 2V: measured: 55° to 60°, calculated: 60° Max birefringence: δ = 0.061 pale blue Max birefringence: δ = 0.020 Max birefringence: δ = 0.008 Max birefringence: δ = 0.016 β = 106° 2V: measured: 83° to 90°, calculated: 84° to 88° Max Birefringence: δ = 0.014 β = 90.46°

Max birefringence: δ = 0.140 2V: measured: 35° calculated: 28° Max birefringence: δ = 0.140 Max birefringence: δ = 0.026 pale green Biaxial (-) nα = 1.585 nβ = 1.604 nγ = 1.612 2V: measured: 65° , calculated: 64° Max birefringence: δ = 0.027 Max birefringence: δ = 0.050 emerald-green Max birefringence: δ = 0.030 apple green Max birefringence: δ =0.047 violet Max birefringence: δ = 0.021 2V: measured: 45° , calculated: 44° Max birefringence: δ = 0.015 α = 91.41(1)°, β = 92.33(1)°, γ = 120.26(1)° Max birefringence: δ = 0.049 Max birefringence: δ = 0.039