More and more rubies are appearing in Thailand with their surfaces "repaired". The process, which fuses a glass substance to the corundum, fills cavities that would have been left after cutting. Since removing such blemishes through cutting would mean a lighter and less valuable finished stone, the technique can mean the difference of profit and loss to this cottage industry.
Microscopic examination easily identifies filled cavities. Immersion in methylene iodide will show a high relief of the filled area and if a refractive index can be taken of the spot in question, a glass reading will be observed. In addition, gas bubbles may very well be present in the filled area.
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- Northwest Gemological Laboratory
- Northwest Gemological Laboratory, Inc. (NGL) is the Pacific Northwest's leading independent appraiser of fine jewelry and gemstones, with state-of-the-art facilities in Bellevue, Washington. Our Graduate Gemologists adhere to the highest gemological standards in the industry, without ethical compromise.
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