Custom cut gemstones, carvings and inlays for jewellery

Between the standard round, oval and cushion and a stone no one else has lies a wide range of cutting. Step cuts in unusual outlines such as hexagons, kites and shields, for geometric layouts. Rose cuts, flat-backed and domed with triangular facets. Buff-tops, with a polished dome above a faceted pavilion. Briolettes, drops faceted all the way round. Fantasy cuts, where facets are scooped or grooved into the stone rather than laid flat, so the light moves through it differently.

What is possible is set by the material as much as by the drawing. A stone’s hardness decides how fine an edge will last; some species, topaz among them, split easily along one direction and have to be cut with that in mind; and the rough decides how large the finished stone can be, and where its colour and inclusions will fall.

Carving shapes a stone as a form rather than as a set of facets: a leaf with its veins cut in, a fluted bead, a cameo raised from a banded agate, or an intaglio cut into the surface, as on a seal ring. Chalcedony, agate, quartz, jade, tourmaline and beryl are among the materials carved most often, chosen for colour, toughness and how they take a polish.

A carving changes how a piece is made. Its back, its undercuts and any drilled holes decide how it can be held, and a carved stone rarely sits in a standard setting. So the carving and the mount are drawn together, and the setter sees the drawing before the cutter starts.

An inlay sets stone level with the metal around it, in a signet’s face, a band or a channel between gold walls. Opaque and translucent materials suit it best: onyx, malachite, lapis lazuli, turquoise, opal and mother-of-pearl. Each piece is cut to the recess it fills, so the metal is made first or both are made to one drawing.

Inlay materials need the same disclosure as any other stone. Most black onyx in the trade is dyed chalcedony, and much turquoise is stabilised to harden it. Several inlay stones are also soft: malachite and turquoise scratch more easily than the metal around them, which matters on a ring worn every day.

A calibrated stone is cut to an exact size in millimetres, such as a 6 × 4 mm oval or a 3 mm round, so that settings can be made before the stones arrive and any stone of that size will fit any seat. For a production run calibration is what makes the hundredth piece the same as the first; for a matched suite it is half of the match, colour being the other half.

Many coloured stones are cut from the rough to keep as much weight as possible, not to a standard size. Such stones are measured one by one and the seats in the model cut to fit them, or they are recut to calibrated sizes, which loses weight and changes their cost.

A cutter works from measurements, not adjectives. A brief that leaves nothing to guess comes back closest to the drawing:

• The outline, drawn to scale, with dimensions in millimetres and the tolerance on each.
• The depth the setting allows, and how the stone will be set: claw, bezel, flush or inlaid.
• The facet pattern or the carving, drawn from the top and from the side.
• The colour, against a reference, and for strongly coloured species the direction it should face up in.
• The species, the treatments you will accept, and whether a laboratory report is needed.
• The quantity, and whether the stones have to match each other.