Gem treatments - Fracture or Cavity Filling

Fracture or cavity filling

– filling surface-reaching fractures or cavities with a glass, resin, wax or oil to conceal their visibility and to improve the apparent clarity of gem materials, appearance, stability, or in extreme cases—to add to a slight amount of weight to a gem. The filling materials vary from being solids (a glass) to liquids (oils), and in most cases, they are colorless (colored filler materials could be classified as dyes).

1. The most commonly encountered fracture-filled gems include:

Diamond – Surface-reaching fractures are sometimes filled with high-lead-content glass. This reduces the visibility of the fracture, with the goal of enhancing the appearance of the diamond. The filled fracture is still present – it is just less apparent.

Surface reaching fractures in diamonds can be filled with molten lead glass, lessening the appearance of the fractures.

Ruby – Numerous surface-reaching fractures are filled with a glass to lessen their visibility and make the gem more transparent than it really is. In some cases, the amount of filler glass can be significant in a treated ruby.

Surface reaching fractures in rubies, such as these, can be filled with molten lead glass, lessening the appearance of the fractures.

Emerald – Surface-reaching fractures in emerald are sometimes filled with essential oils, other oils, waxes, and “artificial resins” —epoxy prepolymers, other prepolymers (including UV-setting adhesives), and polymers to reduce the visibility of the fractures and improve the apparent clarity. These substances have varying degrees of stability in treated emeralds, and the volume of filler material present can range from insignificant to major amounts.

Surface reaching fractures in emeralds, such as this one can be filled with artificial resins, wax, and epoxy polymers. This lessens the appearance of the fractures, as the treated emerald on the right shows.

Other materials – Resins and glasses can potentially be used on any durable gem with surface-reaching fractures, including quartz, aquamarine, topaz, tourmaline and other transparent gems. This kind of treatment is, however, less prevalent than the other treatment processes mentioned above.

2. Durability factors – Much depends on the durability of the filler. Glasses tend to be harder and therefore more durable than resins, oils or waxes. Changes in air pressure, proximity to heat, or by exposure to chemicals can all affect the appearance of filled gems by potentially altering or removing the filler substance.

3. Detectability – In most cases, filled gems can be recognized by a qualified gemologist using magnification.

4. Encountered in the trade – Often encountered for diamonds, ruby and sapphires, and emerald.

5. Special care requirements –Avoid exposure to heat, and changes in air pressure (such as in an airline cabin), or chemicals. Filled emeralds can also be damaged by exposure to hot water used for washing dishes.


Source: Robert Weldon,

To learn more about gem treatments see also:

- An introduction to Gem treatments

- Gem treatments - Bleaching

- Gem treatments - Surface Coating

- Gem treatments - Lattice Diffusion

- Gem treatments - Laser Drilling

- Gem treatments - Irradiation

- Gem treatments- Impregnation

- Gem treatments - High Pressure, High Temperature (HPHT)

- Gem treatments - Heat treatment

- Gem treatments - Dyeing