Glass Infilling Of Cracks In Ruby

(via ICA Lab Alert, No. 4, June, 1987) AIGS writes:

Details
During the ICA Congress held recently in Bangkok, Dr Henri Hanni of Switzerland described to us a new ruby treatment. This consisted of poor quality African ruby cabochons whose cracks had been filled with glass. At the time of the Congress we had not yet seen these stones in Bangkok. In late June of 1987 we saw the first stone. It was a heavily included ruby cabochon, with many cracks that passed deep into the stone. These were filled with glass-like substance. This treatment differs from ordinary surface repaired rubies as the glass dos not just fill in surface pits, but instead appears to penetrate deep into the cracks.

Detection
This treatment is easily detected in the same manner as ordinary surface repaired rubies. Using overhead lighting, or immersion in methylene iodide, will reveal the glass filling due to its different luster or relief. If the opening of the crack is very narrow, however, the glass filling may be difficult to see. Gas bubbles may be found in some of the glass areas.

Dr K Schmetzer writes:
Kenyan rubies are also treated with plastics in order to improve the quality of the stones. In the treatment, cracks or fissures were filled with plastics which is sometimes deeply penetrating into the stones.