URGENT LAB INFO A TREATED STONE SOLD AS ‘BLACK SAPPHIRE’ By GIT Gem Testing Laboratory January 17, 2014
INTRODUCTION One of the GIT’s main duties as the national gem institute is to provide a highly standard gemstone testing service to the country’s gem and jewelry industry. Our gem-testing laboratory (GIT-GTL) has constantly monitoring any new gem material or treatment that comes in the market. Once it was found, we then make a preliminary investigation, and quickly disclose its intrinsic properties and proper name of such material to the gem community. MATERIAL Recently, our GIT-GTL received a parcel of gems sold as “black sapphire” in the market for identification. All of them look very similar in their quality and cutting style. We selected two representative pieces that came in mixed cut oval shapes weighing 1.44 and 1.91 cts for a preliminary study (Figure 1) reported hereafter. On a first glance these two stones appear black but when we observed closely they actually are very dark blue stones. As such the next question that came to our minds was whether these stones genuine or treated. They can be a very dark blue sapphire reportedly found in several localities worldwide, such as those in Shandong province of China or the very deep blue variety of Australian sapphire. These gem materials are usually sold as “Black Sapphire” in the market. On the other hand they can be a newly treated stones as well.
The Gem and Jewelry Institute of Thailand (Public Organization) 140, 140/1-3, 140/5 ITF-Tower Building. 1st - 4th and 6thFloor,Silom Road, Suriyawong, Bangrak, Bangkok 10500 Thailand Tel: +66 2634 4999 Fax: +66 2634 4970; Web: http://www.git.or.th; E-mail: jewelry@git.or.th