This polished 19.25-ct Australian black opal shows the cracks known as “crazing.” © Opal Auctions. Used with permission.

Opal Stone - Natural, Tumbled, Gray, 19.25 ct - International Gem Society

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Opal Stone – Natural, Tumbled, Gray, 19.25 ct

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Opal Stone

This polished 19.25-ct Australian black <a href="https://www.gemsociety.org/article/opal-jewelry-and-gemstone-information/" data-wpel-link="internal" target="_blank">opal</a> shows the cracks known as "crazing." © <a href="https://www.opalauctions.com/auctions/1925ct-polished-black-opal-rub-with-crazing-327256" data-wpel-link="external" target="_blank" rel="external noopener nofollow noreferrer">Opal Auctions</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.

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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;

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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.
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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.

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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.

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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	Australia
Carat Weight	19.25
Gem State	Tumbled
Color	Gray
Transparency	Translucent
Photo phenomena	Play of Color