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912 Live Oak Park Rd South
Fallbrook, CA, 92028
United States

+1 (760) 728-9121

Pala International has consistently earned its reputation as the direct source for the finest colored stones.

AGTA Glass Infilling

AGTA Gemstone Update title image

Lead Glass Fracture Filling in Ruby

In March of 2004 the GAAJ issued a Lab Alert which described rubies that were being treated by a lead glass fracture filling technique. This was followed in July of 2004 with news that stones treated in this manner had entered the US market and further described in Gems & Gemology in the fall of 2004. Over recent months the AGTA Gemological Testing Center has observed an increasing number of rubies treated in this manner and reports from ruby dealers now indicate that significant parcels of these stones are being sold in the US market.

It is important that those buying rubies make themselves aware of the presence of this material on the market. If a stone is suspected of being treated;

  • Examine the stone in reflected light and look for surface reaching fractures
  • In transmitted light look for the p¥resence of flattened bubbles within the fractures
  • In dark-field illumination look for color flashes in the vicinity of fractures (figure 1)

If either flattened bubbles or color ‘flashes’ are seen in the vicinity of fractures, it is likely that the stone has been treated by this new technique.

The majority of lead glass fracture filled rubies examined at the AGTA-GTC have been extensively treated (figure 2). Contact the AGTA-GTC for further information

Tel: 212 752 1717
Fax: 212 750 0930

Ruby Photomicrograph image
Figure 1: Blue ‘flashes’ seen in the vicinity of fractures filled with a lead glass in a ruby
Ruby Microradiograph
Figure 2: The majority of the lead glass fracture filled rubies seen at the AGTA-GTC have been extensively treated; this is clearly revealed in this microradiograph — the lighter gray lines indicate the lead glass inside fractures.


AGTA Gemological Testing Center

18 East 48th Street, Suite 502

New York, NY 10017

Telephone: 212-752-1717

Fax: 212-750-0930

E-mail: Website: