Very fine grained and porous dolornite (around 10 rnicrons of crystalinity) acquire reddish colors with alizarin-S red over polished surfaces. This color can not be distinguished from that of calcitic dolornites when performing the analytical test. In order to avoid this misinterpretation alizarin-S red was dropped (3 or 4 drops) over fme powdered dolomite. Few rniligrams (10 to 15 mg) of the powder are enough for this test.
