Dolomite

MgO promotes the formation of a stable, low-viscosity glass phase at high temperatures, improving densification and reducing porosity. It also reduces the thermal expansion coefficient of the ceramic body, improving thermal shock resistance — particularly important for floor tiles and sanitaryware.

Calcium carbonate provides only CaO upon decomposition, while dolomite (CaMg(CO₃)₂) provides both CaO and MgO. The dual flux action of dolomite is preferred when both thermal shock resistance (from MgO) and vitrification (from CaO) are required in the same ceramic body formulation.

Dolomite begins decomposing between 700–900°C, releasing MgO and CaO progressively. MgCO₃ decomposes first (~750°C), followed by CaCO₃ (~850–900°C). This staged decomposition must be complete before the ceramic body reaches its peak densification temperature.

Yes. Dolomite is used in raw-batch glaze formulations as a source of both CaO and MgO flux. MgO in the glaze promotes matte or satin surface effects, improves chemical durability, and contributes to thermal expansion matching between glaze and body.

High-purity dolomite grades like MICRON CARB DL, with controlled iron and colouring impurity levels, do not adversely affect the whiteness or firing colour of ceramic bodies. Impurity control is essential to avoid discolouration in white or light-coloured tile and sanitaryware bodies.