Question: I was told years ago that natural rubies fluoresce but lab-grown rubies won’t. Recently, someone told me the opposite. He says that synthetic rubies fluoresce but natural stones won’t. Can you settle this?
By International Gem Society 2 minute read

This ruby crystal on a zoisite matrix has a cherry-red fluorescence under ultraviolet (UV) light. Mundarara Mine, Arusha Region, Tanzania. Photos © Rob Lavinsky, Used with permission.

Answer: All rubies fluoresce, whether they’re mined or created in a lab, since natural and synthetic ruby gemstones have the same chemical composition and physical properties. However, there are slight differences in fluorescence patterns between natural and synthetic stones and even between natural rubies from different sources.

Fluorescence of Rubies from Various Sources

For example, flame fusion is the most common way to synthesize corundum gems, which includes rubies and sapphires. Flame fusion rubies fluoresce stronger than natural gems. This can be used as a clue during identification.

In practice, it’s sometimes a very difficult determination to make. However, when you have a tiny stone that doesn’t yield much information, every little bit helps.

The following is an overview of how some rubies fluoresce under longwave (LW) and shortwave (SW) UV light.

  • Myanmar (Burma) Rubies: LW strong red. SW moderate red.
  • Sri Lanka (Ceylon) rubies: LW strong orange/red. SW moderate orange/red.
  • Thai rubies: LW weak red. SW inert.
  • Flame fusion rubies (synthetic): LW very strong orange/red. SW moderate to strong orange/red.
  • Flux-grown rubies (synthetic): LW Strong orange/red. SW orangey red and may have a blue tint or areas of blue.

I hope this helps to clarify things for you,

Don Clark, CSM IMG

rubies fluoresce - Myanmar

Ruby crystal with brilliant red fluorescence, 1.5 x 1.2 x 1.1 cm. Kadottat, Mogok, Sagaing District, Mandalay Division, Myanmar. Photos © Rob Lavinsky, Used with permission.

Additional Comments on “Do Natural Rubies Fluoresce?” from the IGS on Facebook

rubies fluoresce comparison - Jeffery Bergman, Primagem

© Jeffery Bergman, Used with permission.

Natural rubies fluoresce a bit. Natural Burma rubies GLOW!

Elaine Hochberg

The fact that raw hexagonal ruby crystals can fluoresce, and crystal cross-sections in matrix can also fluoresce, is a definitive answer.

Angel Brick

I have a number of rubies from Burma that are natural and light up like a Christmas tree under UV light, like the rubies that Jeffery shared on this post. I can’t speak about synthetics since I’ve not tested one under UV light.

Jerry Anderson Jr.

Don’t forget that synthetic rubies have the same physical, chemical, and optical properties of a natural ruby so both fluoresce, but Burmese rubies more so, definitely.

Jennifer Simonds

This ruby crystal on white marble matrix displays outstanding fluorescence. 2.9 x 2.6 x 1.1 cm, Nangimali, Neelum Valley, Azad Kashmir, Pakistan. © Rob Lavinsky, Used with permission.