Abstract

The visual differentiation between the different mineral constituents in a carbonate rock is fundamental to most studies of carbonate petrography, correlation and genesis. Differential staining of the constituent minerals provides a rapid means of recognizing the textural and compositional differences in the rock. This contrast between the component minerals can be accentuated by etching prior to staining. For routine identification of carbonate minerals, alizarine red S and Harris' hematoxylin stains are recommended, since they are fast, efficient, and dependable. For dolomitic rocks, the following 20 organic dyes provide a wide choice of colors for staining: Titan Yellow, 4(p-Nitrophenylazo)-1-naphthol,Quinalizarin, Alizarine Cyanine Green, Rhodamine "B" Base, Benzopurpin 4B, Congo Red, 1, 5 Diphenylcarbolhydrazide, Alizarine Red S, Barium Eosinate, Trypan Blue, Safranine O, Anthraquinone Green G (and Green G Base), Janus Green B, Bismarck Brown Y, Carmine Cert., Orange G, Neutral Red, Hastings Light Fast Violet, and Celutate Brilliant Blue. A combination of two different stains alizarine red S and Feigl's solution, can be used in differentiating dolomite, calcite, aragonite, high-Mg calcite, gypsum, and anhydrite. Organic dyes stain calcite in acid solution and dolomite and magnesite in basic solution. The period of immersion in a staining solution, the acidity or alkalinity and temperature of the solution (i. e., whether the solution should be boiled or not) vary with the composition, porosity and grain size of the material to be studied. Because preparation and use of the solutions do not require laboratory facilities, the staining experiments may be conducted in any geological office on cores and cuttings for quick and accurate identification of these minerals. Outlines of recommended staining procedures are given in tabular form.

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