Mounted-Stone Dop — Holding a Set Stone for Refacet or Repair
Mounted-Stone Dop — Holding a Set Stone for Refacet or Repair
Specialised dop allowing repolish or recut of a stone without unmounting from its setting
A mounted-stone dop is a specialised type of dop stick designed to hold a gemstone that is already set in a finished or partially-finished mounting, allowing the lapidary to recut, refacet, or repolish the stone without removing it from its setting. Conventional dopping technique adheres the stone directly to the dop with a hot wax or epoxy adhesive, an approach that requires the stone to be free of any surrounding metalwork. Mounted-stone dopping addresses the common service-trade scenario in which a client requests repair or refurbishment of a stone in situ — typically because unmounting and remounting carry their own risks of damage to the stone, the setting, or both.
Construction
Mounted-stone dops typically take the form of a side-clamping or adjustable-collar mechanism that grips the metal mounting itself rather than the stone, with the gripping surfaces lined with soft material to avoid damage to the metal finish. The dop body provides the same standard interface to the faceting machine as a conventional dop. Several designs are in commercial production and additional designs are commonly fabricated by individual lapidaries to suit specific repair scenarios.
The gripping mechanism may be a screw clamp, a spring-loaded collet, a wax-and-clamp combination, or a custom-fabricated cradle. The choice depends on the geometry of the mounting (a band ring, a pendant with a bail, a brooch with a pin) and the specific operation to be performed. Light fingertip-pressure adjustment is generally required to optimise alignment without distorting the mounting.
Use cases
Mounted-stone dopping is the appropriate technique for several common service scenarios. Light chipping of the table or crown of a faceted stone in a setting can often be repolished without unmounting, particularly if the chip can be reached through the table and the surrounding metalwork allows tool access. Recutting of a damaged pavilion or culet may be possible without unmounting if the setting design permits access to the relevant facets. Refurbishment of a worn or damaged polish on the table of a stone in a setting can be performed by careful repolish work with the stone mounted.
Conversely, several scenarios specifically rule out mounted-stone dopping. Major recutting operations that require complete realignment of the stone (such as substantial weight loss to remove deep damage) generally require unmounting because the new geometry is unlikely to align with the existing setting. Setting removal followed by full unmounting is preferable when the stone has been moved or stressed in the setting and requires examination of the pavilion side.
Precision and risks
Precision alignment is critical to mounted-stone work. Any misalignment between the dop axis and the original facet pattern of the stone produces asymmetry in the recut, with cosmetic and optical consequences that may be worse than the original damage. Lapidaries undertaking mounted-stone work require both faceting skill and an understanding of metalsetting structure to avoid causing damage to the setting itself during the operation.
The risks of mounted-stone work — accidental damage to the stone, damage to the surrounding mounting, alignment errors, time required compared with unmount-and-remount — should be discussed with the client before the work is undertaken. For high-value pieces, the conservative recommendation is often to unmount, perform the lapidary work cleanly, and then reset, accepting the additional time and cost in exchange for the reduction in risk.
References
Mounted-stone dopping is described in standard faceting references including Glenn Vargas's Faceting for Amateurs and is a topic in advanced faceting workshops at gem-trade schools and societies. Custom dop designs and trade techniques are exchanged through the lapidary trade press and at gem-show workshops.