Step 3: Practical Gemology

Lesson 23

Gems are frequently dyed to enhance their color. Distinguishing natural from enhanced stones is an essential skill for gemologists. The materials used for dye testing will vary with the gems you’re examining, but the procedures remain essentially the same.

Exhaust The Alternatives Before Dye Testing Gemstones

You can often distinguish dye in a gem with a microscope. See Identifying Inclusions Found in Enhanced Stones for more information on this. Remember, dye testing is a destructive test, so always examine your specimen with a microscope first. The testing procedure presented here is a last resort in cases where the microscope exam proves inconclusive.

Frequently Dyed Gemstones

Many soft, porous gems are often dyed. Lapis lazuli is one of the most common recipients of dyes. Any dark lapis is suspect and needs testing. The same holds true for turquoise.

Gemstone Dye Testing Procedures

  • Choose an inconspicuous location on your specimen for your test. (If the stone is faceted, choose a point near the girdle).
  • If you’re testing a strand of beads, make sure you don’t get any fluid on the cord. Some of the chemicals used for identification