girdling

In gem cutting, girdling refers to rounding a diamond into a cone shape by placing it in a lathe and holding a second diamond against it as it spins. The girdle is the widest part of a faceted gemstone, separating the crown (upper portion) from the pavilion (base).12

Gem cutting is a specialized art that transforms raw gemstones into beautiful, durable pieces. This process involves several steps, including marking, cleaving, sawing, girdling, and faceting. Faceting involves creating flat, polished surfaces on a gemstone to enhance its brilliance through the refraction and reflection of light. While some gems are cut en cabochon (with a rounded upper surface), faceting is crucial for transparent gems like diamonds, sapphires, and rubies to maximize their beauty. Assembled gems, like doublets and triplets, are created by cementing together multiple pieces to form a larger, more valuable stone.1234