Gem Carving: Materials and Techniques

Semiprecious hard stones such as carnelian, chalcedony, amethyst, and agate have long been carved with decorative and figural designs.

As early as 5000 B.C., craftsmen in Mesopotamia used hand-powered tools to engrave images into stone blanks, creating intaglios (so called from the Italian intagliare, "to cut into"). Similar methods were employed by ancient artisans in Egypt, Greece, Rome, and Etruria.

Intaglios were used to make relief impressions when pressed into wax, clay, or another sealing material.

Around 250 B.C. a new carving technique developed: by cutting away the area surrounding a figure, artisans formed relief images known as cameos. The different hues of banded stones were exploited to enhance the appearance of depth with multicolored compositions.

diagram of cameo and intaglio carving techniques detail of an ancient cameo showing the variation in stone color

Carving Tools
Although intaglios are concave and cameos are convex, both are produced in a similar fashion. A cutting tool dipped in a slurry of abrasive powder and oil is turned while a gemstone is manipulated against it. Cutters of different shapes and materials can be used—drills, wheels, cones, and balls made of copper, bronze, iron, or something softer such as wood or even reed. It is the powder (emery or corundum in antiquity, diamond dust today) carried by the tool, not the tool itself, that actually carves the stone.

This engraving depicts an 18th-century carver along with a variety of cutting tools. The instruments used by ancient carvers were similar, being turned by a bow rather than a foot pedal.

Engraving of an 18th-century gem carver at work