Alizarin Red S staining differentiates calcite from dolomite: calcite stains red/pink, while dolomite remains unstained (colourless). A second stain, potassium ferricyanide, is used to distinguish ferroan from non-ferroan calcite and dolomite. This staining technique is fundamental in carbonate petrography for identifying dolomitisation, dedolomitisation, and mixed carbonate mineralogy in reservoir and source rock studies.