Emerald Filling: Oil Vs. Resin

Emerald Filling: Oil Vs. Resin

During the mining process of emeralds, micro-fractures occur resulting in decreased clarity and value. This is is why nearly all natural emeralds are refined with either oil or resin treatments. Below, we discuss the differences between both treatments with the hope that it aids you in finding the perfect emerald for you.


Oil-filling is the most common treatment used to refine emeralds, and it can be repeated over the gemstone's lifetime to maintain its appearance.

Types of Oil Used

  • Colourless oils, such as Cedar Wood and Canada Balsam

  • Coloured oils

Why To Choose Oil-Filled Emeralds?
  • Improved clarity of natural stone

  • Improved richness in colour of natural stone

  • Oil can penetrate even the smallest of micro-fractures

  • Oil is a less visible filler due to having a similar refractory index to emerald

The Flaws of Oil-Filling

  • Oil-filled emeralds are more fragile than resin-filled emeralds

  • Oil-filling is an impermanent treatment as oil eventually leaches out from the micro-fractures

  • Due to the fluid nature of oil-filled micro-fractures, repairs, resetting and recutting is a lot harder


    Resin is used as a setting-glue that is injected into the micro-fractures within emeralds.

    Type of Resin Used

    • Opticon, which is a plastic polymer resin

    Why To Choose Resin-Filled Emeralds? 

    • Resin-filling is a lot more stable than oil-filling, making repairs, resetting and recutting a lot easier

    • Improved clarity of natural stone

    • Improved richness in colour of natural stone

    The Flaws of Resin-Filling?

    • Resin cannot fill as many micro-fractures as oil, meaning that the treated emerald's clarity can be decreased

    • Resin can disintegrate and begin to yellow, altering the colour of your emerald over time

      Understanding what to look for when buying an emerald is very important and hopefully this brief description of emerald filling treatments can help you to make an informed decision when choosing your timeless jewel.