Ready-to-use solution Magneson according to MANN (dolomite detection) for use in histology, cytology and in materialography/geology for the detection of dolomite in carbonates. pre-treat the sample with 10% HCl (wetting), then drop on a few drops of the Magneson solution. magnesite: blue smithsonite: uncoloured until a hint of blue MgO is present when the sample turns blue after 30 sec.