The composition of yellow (melanitic) garnets occurring in wine amphorae has been investigated using an electron microprobe. Two distinct compositional groups occur which can be distinguished by their manganese oxide (MnO) and titanium oxide (TiO₂) contents. The origin of the garnets is most probably in the volcanic rocks of the Roman province and Vesuvius area. The eventual concentration of these minerals was made in stream beds or beach sands. Amphorae samples from Yemen, Cyprus, Italy and France were investigated. They are of the Dressel types Ia, Ic, 2-4, and Graeco-Italic form. It is proposed that a more detailed investigation of the problem could lead to an interesting tracer for commercial relations.