SourcingMay 09, 2022
First Diamonds from Sierra Leone’s Tongo Mine Coming to MarketSourcingMay 17, 2022
A New Source in Tanzania Is Producing Cobalt-Blue Spinel
The stones come from a deposit close to Mahenge and have been on the market for several months.
Examples of the cobalt-blue spinel from Tanzania (Image courtesy of Mahenge Gems)
New York—Tanzania’s Mahenge region is known in the gem world for its beautiful red and pink spinel, but the area has begun producing another color recently—cobalt blue.
The newly discovered deposit is about 12.5 miles southeast of Mahenge.
The spinel started appearing on the market late last year, according to wholesaler Mahenge Gems, which was established in early 2020 and has direct access to miners in the area.
The material began arriving in the Mahenge Gems office around late October/early November, Director Wez Barber said.
At the beginning, they thought it was standard blue spinel because of the large size of the crystals.
The leading source of cobalt-blue spinel is Vietnam’s Luc Yen District, known for its vibrant blue material, though those stones tend to be small.
This Tanzanian material, Barber said, is the “best of both worlds”—good quality, clean, saturated stones that are more than 1.5 carats in size, including some as big as 40 carats.
The colors so far have ranged from a denim blue to a vibrant electric blue, Barber noted.
“We bought as much of it as we could lay our hands on, and still are, because it was such nice material,” he said.
The company sent stones to a few different labs to have it confirmed as cobalt-blue spinel.
Related stories will be right here …
The newly discovered deposit is about 12.5 miles southeast of Mahenge.
The spinel started appearing on the market late last year, according to wholesaler Mahenge Gems, which was established in early 2020 and has direct access to miners in the area.
The material began arriving in the Mahenge Gems office around late October/early November, Director Wez Barber said.
At the beginning, they thought it was standard blue spinel because of the large size of the crystals.
The leading source of cobalt-blue spinel is Vietnam’s Luc Yen District, known for its vibrant blue material, though those stones tend to be small.
This Tanzanian material, Barber said, is the “best of both worlds”—good quality, clean, saturated stones that are more than 1.5 carats in size, including some as big as 40 carats.
The colors so far have ranged from a denim blue to a vibrant electric blue, Barber noted.
“We bought as much of it as we could lay our hands on, and still are, because it was such nice material,” he said.
The company sent stones to a few different labs to have it confirmed as cobalt-blue spinel.
Swiss gem lab SSEF analyzed a selection of the material, confirming cobalt as the main coloring element, in combination with iron.
This makes the Mahenge material similar to cobalt spinel from sources in Sri Lanka, Pakistan, and Vietnam, the lab said.
The Tanzanian material contains characteristic inclusions, SSEF noted, like oriented geometric lamellae with interference colors together with lines of fine particles. It said similar inclusions have been found in red spinel from Morogoro in eastern Tanzania.
Through Raman spectroscopy, SSEF also found colorless apatite and clusters of small zircon inclusions.
Because the deposit was discovered fairly recently, it remains to be seen how much material it will produce.
Barber said that in the past six weeks to two months, very little material has been coming through their office, but he also noted there had been little mining activity due to the rainy season and Ramadan.
With Ramadan ending in early May and the rainy season coming to a close, they should soon be able to ascertain how much more material the deposit might produce.
Those interested in the cobalt-blue spinel can contact Mahenge Gems via its website or follow the company on Instagram.
Mahenge Gems will also have the Tanzanian cobalt-blue spinel on display during the upcoming Las Vegas Market Week. Visit them in the Gems pavilion at JCK Las Vegas at Booth 33105.
The Latest
EditorsSep 03, 2026
Q&A: Simon G.’s CEO on Why He Won’t Use AI for Jewelry DesignZaven Ghanimian discussed the value of human craftsmanship and where the implementation of artificial intelligence does work.
Events & AwardsSep 03, 2026
Here Are the First Recipients of Nina Pugliese Memorial Scholarship Jewelers of America also revealed the recipients of the Seymour & Evelyn Holtzman Bench Scholarship and its own scholarship programs.
WatchesSep 03, 2026
Robert Pattinson Joins Jaeger-LeCoultre as Brand AmbassadorThe British actor, known for his roles in “Twilight” and “The Odyssey,” will star in a campaign for the Master Control Chronometre.
Brought to you by
Your Piece Could Be the One Editors Talk AboutSubmit your pieces for a chance to win in this year's competition.
CollectionsSep 03, 2026
Sydney Evan Celebrates 25 Years With 4 New CollectionsThe “Confetti Disco,” “Champagne Cheers,” “Tuxedo,” and “Classic Punk” jewelry collections each capture a distinct spirit of celebration.
Weekly QuizSep 03, 2026
This Week’s QuizTest your jewelry news knowledge by answering these questions.
CrimeSep 02, 2026
CA Jeweler Gets 5 Years in ‘Phantom Rolex’ Ponzi SchemeNelson Holdo of Newport Beach pleaded guilty to multiple counts of felony grand theft and writing bad checks and was sentenced Monday.
AuctionsSep 02, 2026
If You Love Cats, This Jewelry Auction Is for YouCat ladies of the jewelry world, unite. Sandy Lerner’s “significant” collection of cat jewelry and other objects is going up for auction.
Brought to you by
Why More Jewelry Retailers Are Hosting Turnkey Estate Buying EventsRetailers are seeking new ways to attract customers, increase traffic, and create revenue – Estate buying events are a popular solution.
MajorsSep 02, 2026
Messika Names Former Omega Exec as New President, CEO of AmericasArnaud Michon, the former Omega USA President, will now lead Messika’s Americas region during its international development.
Events & AwardsSep 02, 2026
Emerald’s New Owner Introduces ‘Glitter in the Grove’The branding references the back-to-back jewelry shows that new parent company Forge will host in Miami's Coconut Grove this November.
AuctionsSep 01, 2026
UK Woman Uncovers Rare Patek Philippe Watch in Mom’s Jewelry BoxThe stainless steel Patek Philippe “Calatrava” watch from the 1930s sold for nearly $80,000 at a recent Hansons Cornwall auction.
ColumnistsSep 01, 2026
Your Jewelry Marketing Has a Bridal ProblemEngagement rings are important but don’t ignore the customers who are buying jewelry “just because,” Emmanuel Raheb writes.
MajorsSep 01, 2026
Kering Names New Pomellato, DoDo CEOsFormer Pomellato CEO Sabina Belli has been named president of Kering Italia amid a shakeup of Kering's new Jewelry division.
MajorsSep 01, 2026
Anne Marie Shulman Joins GPA GlobalThe veteran luxury packaging executive was appointed to help the company grow its North American business.
CrimeAug 31, 2026
$4M Van Cleef & Arpels Diamond Necklace Snatched From Vienna Museum Once the property of an Egyptian queen, the necklace was part of a larger exhibition of VCA jewelry at the Museum of Applied Arts (MAK).
GradingAug 31, 2026
GIA, Gübelin Gem Lab Confirm New Paraíba Tourmaline Deposit in EthiopiaThe labs’ separate investigations each determined that the East African country is producing copper-bearing tourmaline.
Events & AwardsAug 31, 2026
Wisconsin Museum to Host Jewelry Exhibition“Chicago Collects: Jewelry in Perspective” at the Oshkosh Public Museum will feature works by Fabergé, Lalique, and Louis Comfort Tiffany.
CollectionsAug 31, 2026
Catbird Launches First Men’s Jewelry CollectionThe “Worn Well” collection is Catbird's take on classic men's jewelry.
CollectionsAug 28, 2026
Dolly Parton Would Have Loved This Butterfly Necklace This Buddha Mama butterfly is our Piece of the Week honoring the legend, who embraced the beautiful insect as her symbol.
IndependentsAug 28, 2026
Day’s Jewelers Honored With 3 Workplace AwardsThe employee-owned jeweler was named a “Best Place to Work” in Maine, New Hampshire, and for women.
CollectionsAug 27, 2026
Pandora Expands ‘Talisman’ Collection as Lawsuit Continues The second iteration of the jewelry collection was inspired by the zodiac and the four elements: earth, water, air and fire.
CrimeAug 27, 2026
Customs Seizes Nearly 900 Pieces of Counterfeit JewelryThe package, intercepted in Indianapolis, contained fake Cartier, Tiffany & Co., and Van Cleef and Arpels jewelry.
IndependentsAug 27, 2026
Jessica McCormack to Open First West Coast StoreThe new location in Costa Mesa, California, marks the brand’s second store in the United States and fourth standalone location worldwide.
FinancialsAug 27, 2026
Movado’s Q2 Sales Up As Younger Consumers Take Interest in WatchesThe fashion watch category was once threatened by the Apple Watch, but consumers are now opting for new wearables, said Movado’s CEO.
SurveysAug 26, 2026
5 Jewelry Insights From The RealReal’s Resale ReportThe report delves into trending styles, the most popular jewelry brands by city, and why Belle Époque jewelry could be the next big thing.
Lab-GrownAug 26, 2026
AGTA Now Requiring Members to Call Lab-Grown Gems ‘Synthetic’The association added the requirement to its revised "Code of Ethics" and released the 17th edition of its “Gemstone Information Manual.”
SurveysAug 26, 2026
Consumer Confidence Dips in August Amid Anticipatory Anxieties Respondents were concerned about the future of the labor market and their income as well as the rising prices of gas and groceries.
