There are many ways to cut gems. Opaque or translucent semi-precious stones such as agate or jasper will be rolled, polished, carved, engraved or cut into cambered shapes. Transparent gems such as amethysts, diamonds, and sapphires are generally faceted to optimize the brightness and fire of the gems, or in some cases to enhance the color of the gems. We collectively refer to the process of dressing gems as cutting, although dressing is actually usually done by grinding.
Polishing and engraving
Many semi-precious stones can be rounded and polished by placing them in a rotating jelly. The cylinder will revolve around a long axis, with layers of fine abrasive and water attached to it. This method is called rolling polishing, and the working principle is similar to that of beach pebbles. Layered gems such as onyx and red striped agate have been embossed for more than 2,000 years. In embossing, gems will be cut along the patterned wheels, and they will stand out under the background of different colors. In intaglio, the pattern is cut away, creating a concave image that can be used as a stamp.