Friday, December 4, 2009
Cutting a Rough Stone
Cutting a raw stone into a faceted and polished gemstone is a multi-step process. Each step is critical to the final outcome. The steps are:
Faceting (Cross Working)
Marking: A rough stone is marked prior to cleaving or sawing to determine the direction of the grain or "cleavage", eliminate waste, and bypass inclusions or imperfections. The natural shape of the rough stone will also be a major factor in deciding how to cut the stone.
Cleaving: Cleaving refers to splitting a stone along its grain by striking it. A rough stone is cleaved if there are conspicuous defects and/or inclusions which would prevent it from being made into a single gemstone.
Sawing: The rough stone is cut to a shape that approximates the shape of the finished cut stone but without the facets.
Girdling: The rough is placed in a chuck on a lathe. While the rough stone rotates on the lathe, a second diamond mounted on a dop is pressed against it, rounding the rough diamond into a conical shape. This step is also referred to as rounding or bruting.
Faceting: The cutting and polishing of each facet is accomplished by attaching the stone to a dop stick and pressing it against a revolving lap (see "Facetron" below). During this faceting stage the angles of each facet must be cut in order to maintain symmetry and produce maximum brilliance.
Brillianteering: If the primary Faceting or "Cross-Working" is done by a separate craftsman, the final 40 facets of a round brilliant cut diamond's 58 facets will be cut by a Brillianteer.