A dop cone (also called a cone dop) is a conically shaped dop end or dop stick used in faceting to hold a gemstone by its already-cut pavilion while the crown is being worked. The defining feature is its tapered interior or exterior profile, which is matched to the pavilion angle of the stone so that the pavilion facets seat firmly and evenly within the cone. This geometry distributes the adhesive — typically dopping wax or, in modern practice, cyanoacrylate — across multiple facet surfaces simultaneously, producing a mechanically stable and well-centred grip without obscuring the girdle or the emerging crown facets.

Function and Design

In the standard two-stage faceting sequence, the pavilion is cut and polished first, with the rough held in a simpler flat dop or wax dop. Once the pavilion is complete, the stone must be transferred so that the crown can be addressed. The dop cone is the instrument of that transfer: the finished pavilion is nestled into the cone's cavity, the adhesive is applied, and the assembly is allowed to cure. Because the cone's taper approximates the overall pavilion geometry — typically somewhere between 40° and 45° for standard round brilliants, though specialist cones exist for shallower or steeper designs — the stone is automatically presented at roughly the correct orientation, reducing the time needed to true up the transfer on the faceting head.

The cone must leave the girdle fully exposed. A correctly sized cone contacts only the pavilion facets below the girdle plane, allowing the cutter to establish the girdle thickness and begin the table and bezel facets without obstruction. Selecting the wrong cone diameter is a common beginner error: a cone that is too large will ride up over the girdle, while one that is too small will fail to provide adequate support and may allow the stone to rock under cutting pressure.

Materials

Dop cones are most commonly machined from brass or aluminium. Brass is preferred by many experienced cutters because its greater mass provides thermal stability during wax dopping — the cone absorbs and retains heat evenly, allowing the wax to flow uniformly into the pavilion facets. Aluminium cones are lighter and resist corrosion, making them practical for bench use with cyanoacrylate adhesives, which do not require heat. Some specialist suppliers offer cones in stainless steel for high-precision work, though the additional cost is rarely justified for production cutting.

Cones are produced in graduated series to accommodate different stone sizes and pavilion geometries. A well-equipped lapidary bench will typically hold a range of cone diameters spanning from sub-3 mm (for small melee) up to 20 mm or larger for substantial collector stones.

Use in Transfer Dopping

The transfer process is the critical moment at which alignment errors are most easily introduced. When using wax, both the flat dop holding the finished pavilion and the receiving cone are warmed, the wax is applied to the cone, and the two dops are brought together in a transfer jig — a device that holds both dop sticks collinear and at 180° to one another, ensuring the table will be cut parallel to the girdle plane. Once the wax has cooled and hardened, the original flat dop is released by gentle rewarming. With cyanoacrylate, the sequence is similar but relies on the jig alone for alignment rather than on the thermal properties of the wax.

A well-executed transfer using a properly fitted cone will produce a crown whose table is perpendicular to the stone's optical axis — a prerequisite for symmetrical light return and accurate meet-point faceting.

In the Trade

Dop cones are consumable workshop items rather than precision instruments, and they are widely available from lapidary suppliers. They are sold individually or in sets matched to standard dop stick diameters (commonly ¼ inch and 3/16 inch shanks in the North American market, metric equivalents elsewhere). The cone is considered part of the broader dopping system alongside flat dops, wax dops, transfer jigs, and dopping wax, and is discussed in most standard faceting manuals as an essential component of competent crown work.