Cobalt Blue: The Other Jedi Spinel

Cobalt Blue: The Other Jedi Spinel

They were never cheap, at least not since I have been in this trade. But now the red Jedis, the famous Burmese red spinels, have vanished completely. In Tucson this past February (2023), Yavorskyy Gems was down to just a few dozen boxes and they used to be the market leader in reds, with more choices than any of the other vendors specializing in Burmese spinels. Nomad’s Gems has been out for a while, Dudley B. has been out for years except for the occasional bright melees that are ‘basement mined’ from old stock; my spinel melee supplier is down to a few boxes as well (they bought up a slew of melee in 2019 and are just selling down until done). Many of these gem productions are smaller than you think, far smaller, so for a while the stuff is everywhere and then it goes poof. I was told that a top of the line one carat red Jedi can now go for 20K/ct, but I didn’t see one anywhere at the GJX or the AGTA anyway.

And now that these supplies are finished, people are turning to blue: Vietnamese cobalt spinel from Luc Yen, and the single find of blue cobalt bearing spinel from just south of the town of Mahenge, Tanzania. Spinel with cobalt content can also be found in Sri Lanka, but none of those are neon in any way because they also have too much iron content which makes them greyish. Most of the Luc Yen and Mahenge material isn’t neon blue either, but a small percentage of it is. Prices for cobalt spinel have been at the top end of the colored stone market for years already but the melees have not gone up as much in price as the larger pieces (wholesale for 2 carats can run you $50,000/ct).

To get you a sense of what’s out there and what the colors are like, let me start by comparing cobalt spinel to hauyne.

Facet grade hauyne is mined only in one small area in the world, in the Eifel in Germany, where it is actually a biproduct as the mining site itself is for construction materials. Very tiny amounts are also found elsewhere in the world, but I have never seen facet grade material from any other location on the market. You can read about it on the website which has an extensive database covering locations and discoveries of any mineral you can think of (not just gemmy material). Its strange name comes from a French priest and curator of the Museum of Natural History in Paris. Many people call it 'hauynite' because that’s easier to pronounce.

Hauyne melees are a bit cheaper than neon spinel, clocking in at about 20-30% of the price of the latter. The problem with hauyne is that it has limited use in jewelry. With a hardness of 5-6, the material can easily break when not set into a soft metal such as 18 kt yellow gold. Just like with rhodochrosite, you cannot file the prongs into tips after setting, and you have to pre-bend one prong and slide the gem in, then gently bend the other prongs. Another drawback for hauyne is that the prongs cannot touch the stone (but it also shouldn’t rattle). As a result, the slightest deformation of the jewelry piece will make the gems come out (especially with tiny prong set gems). Bezel setting hauyne is nearly impossible and pave setting causes a lot of breakage (figure on 10%). We always keep a few extra stones in most sizes in case clients do not buy sufficient amounts for setting, and occasionally I have to turn down a setting job when I have sold out of all spares in that size. Hauyne cannot be steamed with too much pressure, as any polishing wheels that are too stiff will scratch the table of the gem. So while I carry hauyne and do occasionally have access to larger stones of ¼ carat or so, I do not want to sell you that size. At the current price tag of up to 10K/ct retail I do not think it advisable to carry them if I also have to offer setting. Who wants to spend 2.5K on a stone that will break? I wouldn’t.

Cobalt spinel, by contrast, has a hardness of close to 8, so the likelihood that a colored stone setter will break it is fairly low. A diamond setter can easily break it of course so when you consult a setter, pick the right one! Most setters are diamond setters because most jewelry is diamond jewelry and diamond setters have very little experience with colored stones except maybe ruby, sapphire or emerald, so do keep that in mind. The other good thing about cobalt spinel is that it doesn’t have any problematic cleavage like kyanite which tends to split in half if a prong is pushed over it along the cleavage lines instead of against it.

In my experience there are two color hues of neon cobalt spinel and one of them is very similar to hauyne. This is a medium vibrant blue that can look almost 100% like hauyne. It is lightly included, which probably enhances the neon color, and occasionally very poorly cut (at least the Vietnamese pieces). The other hue is slightly darker, cleaner, with a wee bit of secondary purple – which turns into a strong purple under incandescent light, so you also get the color change effect.

That is probably my favorite color but the market often demands more money for the more vibrant and slightly included kind. I have seen Mahenge and Luc Yen blue in the more included color and the deeper color tends to come just from Luc Yen (as far as I know, anyway).

There are also lighter colors of cobalt spinel, i.e., a color I would call “powder blue”, it is a very similar tone to the included neon color but lighter and less saturated. You can find this one in our Etsy shop here.

It is not quite as expensive but not cheap either because it still has significant cobalt content. I love that color a lot also and I think that no sapphire looks quite like it. (And now that I said that, no sapphire looks like Jedi cobalt spinel or hauyne, as even the best specimens aren’t that neon.). The sapphire below is on Etsy here. Please contact us directly about the cobalt spinels in the image. 

And finally there are those cobalt spinels who also have a lot of iron content and are more greyish as a result. As you may have noticed, all spinel, now that it has gone mainstream, has significantly increased in price in the last decade. It was made popular by the famous Mahenge find, which was more neon pink than the Burmese reds but quite gorgeous in its own right. Now depleted, attention has turned to other pinks, then the less intriguing grey Burma spinel which is now pretty much finished also. Grey spinel was a biproduct of the more popular pink and red colors and for years it was stockpiled to train cutters with material that could then be discarded. Yes: once upon a time nobody cared about grey spinel. Until a market opened up for it, that is. Now the stockpiles are down and the newer greys are produced in Mozambique. Burmese material is pretty much out of reach, probably largely due to political reasons, though one does hear rumors that there’s not much being mined either. Vietnam spinel continues to be mined but new diffusion and heat treatments are being detected after export and some of my vendors have ceased trying to bring Vietnam spinel to market. The Mahenge find is already partly depleted as it was only one pocket for now, although efforts are ongoing to find more. In the meantime, those who have stockpiled the blues, waiting for the right time to release them, are making them available now until they are sold down.

A final note on the new treatments: I started to hear about heat treatment being effective for spinel about two years ago, and diffusion treatment being successful about one year ago. Efforts to make these treatments work have been made for at least 10 years and may very well have been going on for longer. Since laboratories often lag behind a little in their detection methods or uses for particular gems, it can take a while before these treatments are found in reports or before tests for them are even suggested.

As you can imagine, you cannot trademark a gem treatment in Vietnam (for example), so the way people get an edge on the market is to keep their methods secret and push out as much material as possible until the secret gets out and the treatment is replicated elsewhere, at which point the price for that material drops. That’s pretty much how it works, and it is important for any gem seller but also collector to remain aware of these changes.

As you may know, blue is my favorite color. Mostly I love turquoise blue, like Paraibas, or greenish blues, but I also love vibrant and neon blues with or without purple tint, such as cobalt and royal blue (in sapphire for instance). I have more to offer in cobalt than I have on Etsy so if you want anything let me know. I have two current sources and some private stock, and I continue to invest because I believe it is worth the price. There are no guarantees ever in this market, so take what I say with a grain of salt, but with most of these rarer varieties of colored stones, even a new find can be small and is quickly depleted. You have to play the long game. Most people in this trade put away what doesn’t sell for a while, let the market recover and wait for it to be popular again, then put it out until it’s gone. “Sooner or later everything sells.” That is the motto.