This 15.5-carat double cabochon opal has a flash of color across its entire face. Tsehay Mewcha, Wollo, Welo Province, Ethiopia. © Rob Lavinsky, www.iRocks.com. Used with permission.

Opal Stone - Natural, Cabochon, Blue, 15.5 ct - International Gem Society

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Opal Stone – Natural, Cabochon, Blue, 15.5 ct

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Opal Stone

This 15.5-carat double cabochon <a href="https://www.gemsociety.org/article/opal-jewelry-and-gemstone-information/" data-wpel-link="internal">opal</a> has a flash of color across its entire face. Tsehay Mewcha, Wollo, Welo Province, Ethiopia. © <a href="http://www.irocks.com/" data-wpel-link="external" target="_blank" rel="external noopener nofollow">Rob Lavinsky, www.iRocks.com</a>. Used with permission.

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In 2012, Donald Clark retired and passed along stewardship of the IGS to the Rosen family, who were longtime members of IGS. Lisa Rosen runs the day-to-day operation of IGS and  <a href="https://www.ganoksin.com/">The Ganoksin Project, a technical resource website for bench jewelers and jewelry manufacturers</a>.  Lisa strongly believes that IGS must remain a cost-effective, accurate, and comprehensive resource for all those interested in gemology. IGS is our passion, and it is a family business.

Lisa Rosen

The late Donald Clark, CSM founded the International Gem Society in 1998. Donald started in the gem and jewelry industry in 1976. He received his formal gemology training from the Gemological Institute of America (GIA) and the American Society of Gemcutters (ASG). The letters &#8220;CSM&#8221; after his name stood for Certified Supreme Master Gemcutter, a designation of Wykoff&#8217;s ASG which has often been referred to as the doctorate of gem cutting. The American Society of Gemcutters only had 54 people reach this level. Along with dozens of articles for leading trade magazines, Donald authored the book &#8220;Modern Faceting, the Easy Way.&#8221;

Donald Clark, CSM IMG

Jeffery Bergman, SSEF SGC, founder and director of <a href="http://www.primagem.com/">8th Dimension Gems</a> in Thailand, is an American gem dealer with more than 40 years of experience in gemstone and fine jewelry mining, cutting, wholesaling and retailing. His career has taken him to more than 50 countries and every continent except Antarctica. He has appeared on the BBC, CNN, NBC, ABC and GEO; and has been featured in Time, USA Today, National Geographic, Gems &amp; Gemology and Discovery Channel magazine. He is a regular guest speaker at gem lab seminars and gemological association conferences and universities.

Jeffery Bergman, SSEF SGC

Dr. Joel E. Arem has more than 60 years of experience in the world of gems and minerals. After obtaining his Ph.D. in Mineralogy from Harvard University, he has published numerous books that are still among the most widely used references and guidebooks on crystals, gems and minerals in the world.
Co-founder and President of numerous organizations, Dr. Arem has enjoyed a lifelong career in mineralogy and gemology. He has been a Smithsonian scientist and Curator, a consultant to many well-known companies and institutions, and a prolific author and speaker. Although his main activities have been as a gem cutter and dealer, his focus has always been education. <a href="https://www.joelarem.com/">joelarem.com</a>

Joel E. Arem, Ph.D., FGA

Fatma Oya Borahan, GG, FGG has Graduate Gemologist and Diamond Diplomas from the Gemological Institute of America (GIA) the German Gemmological Association (DGemG) and Gemmological Association of Great Britain (GemA). <a href="http://birdamlasu.com/">birdamlasu.com</a>

Fatma Oya Borahan, GG, FGG

Barbara Smigel is a GIA certified gemologist, facetor, jewelry designer, gem dealer, gemology instructor and creator of the well-regarded educational websites <a href="http://www.acstones.com">acstones.com</a> and <a href="http://www.bwsmigel.info">bwsmigel.info</a>.

Barbara Smigel, PhD. GG

Dr. Gerald Wykoff is GG (Graduate Gemologist), a CSM (Certified Supreme Master gemcutter), educator, and author of several gemology books. He founded the American Society of Gemcutters in the 1980s and served for more than 10 years as the editor of its monthly magazine, American Gemcutter.

Dr. Gerald Wykoff GG CSM

A geologist, environmental engineer and Caltech graduate, Addison&#8217;s interest in the mesmerizing and beautiful results of earth&#8217;s geological processes began in her elementary school&#8217;s environmental club. When she isn&#8217;t writing about gems and minerals, Addison spends winters studying ancient climates in Iceland and summers hiking the Colorado Rockies.

Addison Rice

The late Jeff Graham was a prolific faceter, creator of many original faceting designs, and the author of several highly-regarded instructional faceting books such as <a href="https://rockpeddler.com/product-category/instructional-materials/">Gram Faceting Designs</a>.

Jeff R. Graham

Kyrylo Gubariev, Graduate Gemologist (GG, AJP) is a gemologist with a passion for sharing his knowledge with fellow gem lovers. Originally from Ukraine, he is currently based in Bangkok, Thailand.

Kyrylo Gubariev, Graduate Gemologist (GG, AJP)

Jim Buday was born and raised in Wisconsin. He attended college for biology, but realized that he preferred to work with his hands. He became a general contractor and home flipper. Jim then taught himself to cut gems by watching instructional YouTube videos and reading online forums. By 2019, he was confident enough in his skills to pursue selling his work. He founded the Reddit thread, Shinypreciousgems, which now sits at more than 25,000 members. Jim now works with gems and jewelry full time, and has also partnered with several jewelers to offer settings to his gemstone clients. Recently, Jim started creating his own gem designs. In his free time, Jim enjoys the outdoors, working on his land, and is building a house with his girlfriend, Raeanna.

Gemstone	Opal Stone
Natural or man made	Natural
Origin	Ethiopia
Origin details	Tsehay Mewcha, Wollo, Welo Province
Carat Weight	15.5
Gem State	Cabochon
Color	Blue
Transparency	Translucent
Photo phenomena	Play of Color
Multi-color	more_than_3_colors