A publication of the Archaeological Institute of America
The lapidary engraving wheel, the most important tool for working gems and semiprecious stones, was invented more than 1,000 years later than previously thought, according to British Museum researchers. Formerly the wheel was believed to have been developed during the second half of the fourth millennium B.C. It was thought to have been used to create elaborate Mesopotamian cylinder seals, some of which recounted the adventures of the mythical king Gilgamesh. Seals developed with cuneiform writing and were frequently worn as jewelry. They were often made of semiprecious stones such as chalcedony, rock crystal, and lapis lazuli.
Margaret Sax, Nigel Meeks, and Dominique Collon of the museum's department of scientific research took casts of cylinder seals using dental resin and examined them with a scanning electron microscope. They were then able to build up a chronological table of engraving practice in Mesopotamia and surrounding regions between ca. 3100 B.C. and 400 B.C. Until the middle of the first millennium B.C., quartz seals were usually worked by micro-flaking, a technique in which minute pieces of stone were chipped off with a flint or bronze tool. The study, however, showed that there was no evidence for the use of the engraving wheel before the middle of the eighteenth century B.C.
The introduction of the engraver's lapidary wheel led to the development of new technological and stylistic methods, including the production of seals in harder, more precious stones, says Collon. Engravers were also able to increase their output. The innovation is probably one of a series of improvements in rotary technology at the time, which included the replacement of solid chariot wheels by spoked wheels.