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.

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

The childhood craft of making dried pasta necklaces for Mother’s Day is all grown up as the 14-karat gold “Forever Macaroni” necklace.

Set with May’s birthstone and featuring an earthworm, this ring is a perfect celebration of spring.

“Bridal 2025–2026” includes popular styles and a dedicated section for quick pricing references of lab-grown diamond bridal jewelry.

Supplier Spotlight Sponsored by GIA

Located in Miami’s Design District, the 4,000-square-foot store is an homage to David and Sybil Yurman’s artistic roots.


May babies are lucky indeed, born in a month awash with fresh colors and celebrated with one of the most coveted colored gemstones.

The deadline to apply for the Seymour & Evelyn Holtzman Bench Scholarship is June 12.

Six new retail businesses were selected for the 2025 program, which began in January.

What’s really worrying U.S. consumers isn’t the present situation; it’s what the economy is going to look like six months from now.

Now called The Instore Jewelry Show, it will include holiday-focused education, interactive workshops, and a window display contest.

The “Sea of Wonder” collection features pieces inspired by the ocean, from its waves to flora and creatures like urchins and sea turtles.

The 23-carat fancy vivid blue diamond, set to headline Christie’s May jewelry auction, was expected to sell for as much as $50 million.

G.B. Heron Jewelers in Salisbury, Maryland, is set to close as its owner, Jeff Cassels, retires.

Emmanuel Raheb outlines the differences between the two platforms and posits that the most successful jewelers use both.

The miner said its April sale featured a mix of commercial-quality primary rubies and secondary rubies of varying quality.

U.S. customs agents in El Paso, Texas, intercepted the package, which would have been worth $9 million if the jewelry was genuine.

Health monitors become statement pieces when paired with the brand’s new collection of stackable diamond-studded bands.

Ten organizations were selected this year.

Kim Carpenter and Sam Gevisenheit have joined the brand.

“Shell Auranova” is the next generation of the brand’s bridal line, featuring half-bezel engagement rings with bold and fluid designs.

Boucheron and Pomellato performed well in an otherwise bleak quarter for Kering amid struggles at Gucci.

Designer Deborah Meyers created her birds from oxidized sterling silver, rose-cut diamond eyes, and Akoya Keshi pearl feathers.

The company said it expects sightholders to remain “cautious” with their purchasing due to all the unknowns around the U.S. tariffs.

Sponsored by the Gemological Institute of America

Simon Wolf shares why the time was right to open a new office here, what he looks for in a retail partner, and why he loves U.S. consumers.

A third-generation jeweler, Ginsberg worked at his family’s store, Ginsberg Jewelers, from 1948 until his retirement in 2019.

The company failed to file its quarterly reports in a timely manner.