A Modified Staining Technique for Carbonates in Thin Section

Abstract

POTASSIUM ferricyanide and alizarin red S are frequently used as stains for distinguishing between carbonate minerals. Potassium ferricyanide in acid solution produces Turnbull's blue with ferrous iron and it used to be thought that dolomite could be distinguished from calcite on the basis that dolomite alone contained ferrous iron. Recently this has been shown to be incorrect¹, and it is now known that any carbonate mineral containing small quantities of ferrous iron will stain with potassium ferricyanide providing the carbonate can be made to react with an acid medium. Recent work^2,3 shows that alizarin red S in solution is probably the best method of distinguishing between the common carbonates.