Seals are small, easily portable and often travelled far from their place of manufacture. The raw materials used to make them could also travel, some certainly reaching Crete from beyond the Aegean, while others were evidently confined to specific parts of the island. Tracing the precise sources of the raw materials — including those of Cretan origin — has so far met with limited success.

This paper presents new research which has identified several rare and/or distinctive materials used for Cretan seals from MM II onwards, including banded jasper, red serpentine, fine-grained limestone, and calcite; spondylus shell is also discussed. Certain materials (or more accurately the seals made from them) seem to cluster in eastern Crete — encompassing the sites of Mallia, Mochlos, Petras and Palaikastro. Whether this reflects reality or chance remains to be established. In some cases, clusters are linked not only through material but also through motif and style, suggesting the output of individual workshops, which ultimately may help in the localization of production centres.

The use of these distinctive materials helps to confirm that MM II witnessed considerable experimentation in Cretan glyptic, in which both local and long-distance exchange networks played a significant role. Currently open to question is whether the materials in question were genuinely rare, confined to a specific locale, or were only exploited occasionally, on an “opportunistic” basis. Some materials may have been common enough, but were not much favoured by seal engravers (e.g. because of natural flaws) or by their clientele, who regarded them as insufficiently “attractive”. Nevertheless the existence of these small clusters also chimes with the view that only a tiny percentage of original output has been discovered to date.