Rocks which contain significant amounts of swelling-type clay minerals disintegrate when they are exposed to drying and wetting or to freezing and thawing. The ethylene glycol immersion test is used as a standard test to simulate the breakdown of rocks, containing harmful amounts of expanding clay minerals, when they are used as construction materials in wet and freezing conditions.The glycol test was assessed for petrographic evaluation of argillaceous carbonate rocks intended for use in the construction industry. This was done by conducting the test on 61 small cylinders of a Paleozoic–Verulam argillaceous limestone which contained minor amounts of an expanding clay mineral interstratified with illite and subordinate chlorite. The development and propagation of cracks located in clay concentrations, as seen under a microscope, were used as assessment criteria. Cracks developed very slowly, therefore the test is considered unsuitable for industrial acceptance testing and for petrographic assessment of argillaceous carbonate rocks when quick test results are needed.