Excavations carried out at Cetamura, a small Etruscan/Roman settlement in the Chianti Mountains, have yielded a small quantity of internal red-slip cookware (IRSC, also known as Pompeian red ware) pans and lids. This variety of pottery, manufactured from the third century B.C. to the second century A.C., was the earliest of the mass-produced export cookwares that came to proliferate during the Roman Empire. A program of mineralogical analysis involving low-power microscopic examination, refiring, and petrographic analysis shows that the group of materials from Cetamura includes vessels belonging to three distinct fabric classes. Fabric Class 1, by far the most common at the site, contains clastic materials and appears likely to have been produced somewhere in northern Etruria during the second century B.C. This is a result of some interest, since it has been widely assumed that the early centers of IRSC production were located in the Bay of Naples area. Fabric Classes 2 and 3, both rare at Cetamura, contain volcanic materials and are likely to have been produced somewhere in southern Etruria, the Rome area, or the Bay of Naples area during the second century B.C. and first century A.C., respectively. The mineralogical composition of all three fabric classes suggests that IRSC workshops may have exploited clay sources that yielded base-clays particularly well suited for the manufacture of cookwares. Further such studies may permit the reconstruction of broader patterns in the production and distribution of this class of pottery.