Carbonate refers to the salt containing CO32-. Generally, carbonates are not as stable as other common salts (such as sulfate and halide). Only carbonates of active metals (all alkali metals and barium, strontium, etc.) are not easily decomposed, and the rest of the salts are decomposed when heated to the melting point. The less active the metals are, the lower the decomposition temperature is, and the products are corresponding metal oxides and CO2.

Carbonate can be divided into three types: normal salt M2CO3, acid salt MHCO3 and basic carbonate M2(OH)2CO3(M is metal). Natural carbonate minerals include calcite, aragonite, magnesite, dolomite, siderite, rhodochrosite, smithsonite, galena, strontium carbonate and witherite. Carbonate and acid carbonate (also called bicarbonate) are mostly colorless. Carbonates of alkali metals and ammonium are soluble in water, while carbonates of other metals are insoluble in water. Sodium bicarbonate is less soluble in water, and other acid carbonates are easily soluble in water. Metal ion carbonates containing hydroxide groups are called basic salts and are double salts. Important ones are basic copper carbonate [CuCo3 Cu (OH) 2], basic lead carbonate [2PbCO3 Pb (OH) 2], natural azurite [Cu3(CO3)2(OH)2], malachite [Cu2(OH)2CO3] and so on.