Much of my business comes from re-cutting colored gems that have been chipped, scratched and broken (not always by the goldsmith). Replacing broken in lay material is another favorite.
I know there will always be a need for cutting and polishing (re-cutting) damaged and worn stones but there are ways to cut down the cost of repairs. Let’s start with colored stones.
Obviously, you need to be careful around stones with a file but some stones are more fragile than others are. Any Quartz like Amethyst and Citrine (7on the Mohs scale) will readily chip because they are brittle and sensitive to shock and heat.
Sapphire is a wonderful gem that doesn’t cause too much trouble. It will normally hold up to a file but not a diamond disc. With care, re-tipping can be done without removing the stone.
Apatite is extremely soft (5 on the Mohs scale) and heat sensitive, and breaks offin large chunks under low heat following its 2 cleavage planes.
Tanzanite is soft (6-7 on the Mohs scale) and cleaves in one unpredictable direction. I re-cut a lot ofthese because of wear.
Garnets (probably the last gem that hasn’t been synthesized to the extent of many others) register from 6.5 to 7.5 on the Mohs scale. They have no cleavage and are somewhat brittle so tend to chip easily.
When a stone needs to be re-cut there are just a few things you need to know. Rarely is it possible to cut a scratch out of the table of a stone without removing the stone from the mounting. It can be done but it usually results in a poor job. Some times the wear marks or scratches only go a little way down the stone. Under no circumstances can this stone be repaired without removing it from the mounting. Cabochons can be re-cut and polished in the mounting, but the end result looks like Friar Tuck’s haircut. The scratches cannot be removed completely without damaging the bezel or prongs but the top can be polished back to a high shine.
Filigree settings sometimes contain tiny accent stones that are easily lost or damaged. When these need to be replaced, it is far less expensive to supply your professional cutter with a slightly larger stone of matching color that can be cut down. Repair is generally not an option in these cases because the stones are usually broken. While most cutters can provide the material it will be more expensive. You might want to call your cutter before sending off the job to be sure he/she can cut the size and shape stone you require, as not all cutters will work with really tiny pieces.
Last, but not least, there are some special considerations for inlay pieces. When sizing an inlaid ring, pull the stones when ever possible. Over half of the onyx, lapis and opal inlays I replace have been broken by sizing. Many are epoxied into the setting and careful, gentle heat with plenty of ventilation will enable you to remove it. The solvent “Attack” works well, too, the process is safer but slower for those heat sensitive stones.