Sulfate carbonate

The sulfate carbonates are a compound carbonates, or mixed anion compounds that contain sulfate and carbonate ions. Sulfate carbonate minerals are in the 7.DG and 5.BF Nickel-Strunz groupings.

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

In some structures carbonate and sulfate can substitute for each other. For example a range from 1.4 to 2.2 Na₂SO₄•Na₂CO₃ is stable as a solid solution. Silvialite can substitute about half its sulfate with carbonate and the high temperature hexagonal form of sodium sulfate (I) Na₂SO₄ can substitute unlimited proportions of carbonate instead of sulfate.

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