How to Detect Leaded Glass Treated Rubies?

Gems have been treated for centuries, and some of the treatments are commonly accepted in the jewellery trade and by gemmologists.

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5 min

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Gem-related Field

How It Works
First, let us remind you how this method works: it all starts with the preforming of rough ruby to eliminate matrix and other impurities. Then, depending on the ruby type, the rough is heated up to 900° - 1,400°C. After this first treatment, the red preforms from the previous steps are now packed in a crucible with lead and silica-rich oxide powders, and heated another time to temperatures around 900° to 1000°C.

Details of this ruby pair:

Shape & Cut:
Stone type:
Weight (cts):
1.04 / 0.97
Dimensions (mm):
6.10 x 5.10 x 3.80 / 6.1 x 5.00 x 3.60
Tokyo Gem Lab
How To Detect This Treatment?
That being said, you have to know that it is quite difficult to distinguish this specific treatment in rubies. Unfortunately, the stones don't demonstrate any results under ultraviolet analysis. Actually, the safest way to recognize this method is by using an energy dispersive X-ray fluorescence (ED-XRF). However, only well-equipped labs have these machines. It is then safer to buy a ruby with a certificate if you are unsure about its potential treatment.
Another simpler way (when the treatment is prominent and visible in the stone) to verify whether rubies are treated with glass is to check the lighter colour lines and if there are any internal gas bubbles (single spheres or bubble clouds), as they do not appear in #natural rubies.
Unheated Ruby Mozambique Pair 1.04 + 0.97 cts

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Benjamin Poudevigne
Social Media Manager at GemMatrix
With over ten years of marketing experience, I finally decided to settle down in Bangkok to work in an area that I have always been interested in: the gemstones industry. I'm still learning how the market works on a daily basis, and I enjoy sharing my experience with those who are interested in learning more about gems in general.