Abstract: A significant amount of synthetic moldavites has recently appeared on the precious stones market. Moldavites belong to a large group of tektites-material formed by large meteorites impacting the earth surface. Enormous energy of impact at a speed of minimum 8 km/s caused gasification and melting of the meteorite crater rock basement (so called astrobleme) and especially blowing out a part of the mass into the upper parts of the atmosphere (partly even into the space) and falling back hundreds of kilometres away. The original moldavites crater is by Nördlingen near Stuttgart in Germany, whereas the strewn field is about 300-400 km far in South Bohemia in the Czech Republic, rarely in Moravia. Most synthetic moldavites have unusually high lustre in comparison with natural moldavites. Natural moldavites normally have a very sharp surface (especially those originating from sand sediments). On the contrary, moldavites after water transport have smoothed surface. Edges between the sculptation projections in case of synthetic moldavites are often partly smoothed and the surface is markedly more lustrous (lustre obtained from the acid) or, by contrast, notably duller. Sculptation on synthetic moldavites was created by several methods. The best one, i.e. most resembling natural moldavites, is sculptation caused by selective dissolving in hydrofluoric acid. An ideal distinguishing mark is presence of lechatelierite in natural moldavites. Lechatelierites often project from the surface of natural moldavites (well visible with a magnifier or microscope), and in cut stones, these can also be seen with a magnifier or microscope. In disputable cases, Raman or UV-Vis spectrometry can be used. Fluorescence of synthetic moldavites in long-wave UV (366 nm) is also significant. On the contrary, natural moldavites are completely inert. Measurements results of synthetic and natural moldavites are sufficiently different.