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.
More on Sourcing
The Latest
AuctionsMar 25, 2025
Christie’s To Auction 35-Carat Sapphire, 13-Carat RubyThe ruby and the sapphire, which Christie’s calls a “once-in-a-generation masterpiece,” are part of the upcoming Hong Kong jewelry auction.
CrimeMar 25, 2025
Tiffany & Co. Earrings Swallowed Following Grab-and-Run Theft RecoveredThe two pairs of earrings, snatched from a Tiffany & Co. store in Orlando, Florida, are valued at a combined $769,500.
ColumnistsMar 25, 2025
The Smart Lab: Using Short-Form Videos to Sell More JewelryThe time to start experimenting with video content is now, writes columnist Emmanuel Raheb.
Brought to you by
The Heart of the Industry: Giving Bench Jewelers the Recognition They DeserveBench jewelers spend years honing their skills, Jewelers of America’s Certification validates their talents.
CollectionsMar 24, 2025
Pomellato’s Latest ‘Nudo’ Collections Revamp its Classic DesignFrom striking high jewelry to miniature fine jewelry, the new chapter continues to highlight gemstones featuring its signature 57-facet cut.
Weekly QuizMar 21, 2025
This Week’s QuizTest your jewelry news knowledge by answering these questions.
MajorsMar 24, 2025
4 Top Executives to Depart Signet Jewelers Amid TurnaroundThe jewelry giant is reducing its senior leadership by 30 percent as part of its new turnaround strategy.
WatchesMar 24, 2025
Sotheby's Now Offers Watch Repair ServicesThe auction house's partnership with online watch servicing platform WatchCheck makes repairs convenient and accessible, it said.
Brought to you by
Natural Diamonds Should Mean MoreNatural diamonds mean more than lab-grown, but when every cut is ideal, they all look the same. Customers want more—Facets of Fire delivers.
FinancialsMar 21, 2025
Swarovski Says Its Lab-Grown Diamond Sales Doubled in 2024The company also noted record sales in the United States and a strong performance in its jewelry category.
TrendsMar 21, 2025
Piece of the Week: Marrow Fine’s ‘Til Death’ RingAfter the black enamel band became a best-seller for the brand, it has now launched an enamel ring personalization program.
IndependentsMar 20, 2025
Korman Fine Jewelry’s New Store Is Double the Size The Austin, Texas, jeweler’s new 11,000-square-foot store is set to open this summer.
Events & AwardsMar 20, 2025
JCK Rocks to Feature Snoop Dogg, Jason DeruloThe rapper and singer-songwriter will perform at Tao Beach on June 8.
TechnologyMar 20, 2025
Chris Ploof, Severine Ferrari Launch YouTube Video Series“Conversations with Chris Ploof” covers tips for men buying wedding bands, behind-the-scenes footage of Ploof in his studio, and more.
Lab-GrownMar 20, 2025
Beyond Jewelry: Possibilities in the Lab-Grown Diamond SectorAs lab-grown diamond brands pop up across India, academics are researching how to grow demand outside of the jewelry industry.
MajorsMar 19, 2025
Signet Jewelers to Close Stores, Cut Staff Amid Declining SalesThe moves are part of the retailer’s new turnaround plan, “Grow Brand Love,” which also includes emphasizing brand loyalty over store banners.
CollectionsMar 19, 2025
Jessica McCormack’s New Collection Elevates Office WearThe “Rush Hour” campaign stars Zoë Kravitz in bold, wearable pieces designed to make a statement in the workplace.
WatchesMar 19, 2025
Breitling Acquires Another Watch Brand From the 1800sBreitling is reviving Gallet, which was founded in 1826 and is known for making watches used in the early days of long-distance travel.
AuctionsMar 19, 2025
10-Carat Fancy Vivid Blue Diamond Expected to Sell for $20MDubbed the “Mediterranean Blue,” this “remarkably rare” diamond will be part of Sotheby’s May jewelry auction in Geneva.
MajorsMar 19, 2025
AGS Adds New Program, Relaunches CSAThe American Gem Society now offers a Jewelry Evaluation Advisor designation as well as an updated Certified Sales Associate designation.
CollectionsMar 18, 2025
Beck Debuts New Collection as Trove’s Latest Designer-in-ResidenceRebecca Zeijdel-Paz created more than 75 new pieces for the residency, which will be on display at Trove’s store in New York through April.
ColumnistsMar 18, 2025
Peter Smith: The Importance of Culture in HiringSmith explores why a qualified candidate might still not be right for the job.
Events & AwardsMar 18, 2025
Fink’s Jewelers Is Now a Regional Emmy WinnerThe company and its marketing agency, Loudr, were recognized for the “Make You Dance” marketing campaign.
WatchesMar 18, 2025
Citizen Announces New Modern Luxury Watch CategoryThe “Series8” and “Attesa” collections will be grouped under Citizen Premier.
MajorsMar 18, 2025
Borsheims Names New Assistant IT ManagerDavid Fager, a former systems engineer at the retailer, was promoted to the role.
Events & AwardsMar 17, 2025
Gem Awards Honor All Facets of the IndustryFrom retailers to designers and the media, the fine jewelry industry recognized one another’s work and looked to the future.
Events & AwardsMar 17, 2025
GIA Names Winner of Emerging Jewelry Design Talent AwardEleanor H. Yeh is the recipient of the eighth annual Gianmaria Buccellati Foundation Award for Excellence in Jewelry Design.
MajorsMar 17, 2025
Tous Names U.S. Managing Director, VPJoseph Cavalcante takes on the dual role as the Spanish jewelry brand looks to expand further into the U.S. market.
