Thaumasite Value, Price, and Jewelry Information

What is Thaumasite?

Thaumasite belongs to the ettringite mineral group. None of these minerals appear commonly in jewelry, but thaumasites and ettringites themselves are the most likely to be faceted.

Does Thaumasite Make a Good Jewelry Stone?

You're more likely to find cut thaumasites in rare gem collections than jewelry collections. They have a hardness of only 3.5, which makes them very susceptible to scratching. (However, they seem to harden after exposure to air). Combined with their lack of dispersion, they just don't make very practical or desirable jewelry stones. Any thaumasite in jewelry should have a protective setting and is best reserved for occasional wear.

Prior to the discovery of facetable material in South Africa in the 1980s, gem cutters sometimes cut cabochons from compact, massive thaumasite. Some of these cabs show an interesting but relatively weak cat's eye effect.

Identifying Thaumasites

Thaumasite has a very low specific gravity (SG) of 1.91. Thus, it will always feel light for its size.  An SG test should eliminate most possible misidentifications. However, some other rarely encountered gems with low SG and hardness values as well as similar color ranges include ettringite, gaylussite, inderite, kurnakovite, and ulexite. Of these gems, ulexite is probably the most frequently encountered in jewelry or gem collections. 

Thaumasite has high enough birefringence that some cut gems may show facet doubling.

Thaumasite rough and cut set, 0.7 x 0.4 x 0.4 cm (crystal), 1.11 cts, 9.67 mm x 5.08 mm, cut corner rectangle (gem), N'Chwaning Mines, Kuruman, Kalahari manganese field, Northern Cape Province, South Africa. © Rob Lavinsky, www.iRocks.com. Used with permission.

Are There Any Synthetic Thaumasites?

Scientists have synthesized both thaumasite and ettringite for research into a form of cement deterioration. However, there's no known jewelry use for this lab-created material.

There are no known gem enhancements for thaumasites.

Where is Thaumasite Found?

To date, the only facetable thaumasite comes from the Kalahari manganese field in Northern Cape Province, South Africa.

Other notable sources include the following:

• United States: Cochise County, Arizona; Crestmore, California; Paterson, New Jersey (fine crystals); Centreville, Virginia (in masses); Beaver County, Utah.
• Långban, Sweden.

Stone Sizes

Found as relatively compact fibrous masses up to a few inches in size.

How to Care for Thaumasites

Store any thaumasites separately from other harder gemstones to prevent contact scratches. Clean them only with a soft brush, mild detergent, and warm water. For care recommendations, consult our gemstone jewelry cleaning guide.

Joel E. Arem, Ph.D., FGA

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. joelarem.com

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International Gem Society

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