Geochemistry, isotopic analysis of carbon and oxygen, polarized light microscopy, and electron microprobe analysis provide clues to authenticity in the study of calcite and dolomite marbles and their weathering characteristics in various marine and terrestrial environments. The author describes the use of these techniques with marble sculptures in the Getty Museum. An archaic Greek kouros made of dolomitic marble was found to have a weathering crust composed of calcite formed through a natural process in which magnesium atoms are slowly replaced by calcium atoms (dedolomitization).