Collection: 2025.4.2 The profound cobalt spinel

Good morning, this is Nori-chan.

~ Introduction ~

GemTreeJapan entered the Vietnamese market in 2024 and has since cut numerous sapphires, spinels, and other gemstones. Among these is a sparkling blue gemstone.

When Ilmo first mentioned going to Vietnam , Nori-chan had already requested cobalt spinel. Of course, we are aware of cobalt spinel from other sources, but we cannot leave out the Vietnamese, which has a strong neon feel that is the best.

As I had expected, when I went to the site and made contact between Ilmo-Nori, I was told that even if you purchase locally without going through an intermediary, beautiful items are rare and highly valued, so they are traded at high prices.

Now, in addition to Vietnamese produce, we also handle Tanzanian produce.

Since we have the opportunity, let's write an article about what this cobalt spinel is.

~Cobalt spinel as a mineral~

The photo above shows three stones: iron and cobalt (Vietnam), cobalt only (Vietnam), and cobalt only (Tanzania). The colors vary depending on the elements contained, their proportions, and their origin.

What is this cobalt spinel? Generally, it refers to spinel containing cobalt, giving it a vibrant blue color .

The following two elements are responsible for spinel's blue color.
・Iron ( Fe ) / Cobalt ( Co )
The one that turns blue due to iron is called blue spinel, and the one that turns blue due to cobalt is called cobalt spinel ( *1 ).

*1 Cobalt spinel is a commercial name. It is a common name that is not listed as a gemstone name in sorting or appraisal certificates. Cobalt spinel is generally listed as "blue spinel" on appraisal certificates, with a comment stating that it "contains cobalt."

There is one thing to note here: this is a spinel that contains both iron ( Fe ) and cobalt ( Co ).

This time, we will explain using the notation provided by the Japan-German Gemological Institute. There are two ways to write comments for spinel containing two elements:
(A) Iron bands and cobalt bands are permitted.
(B) Cobalt bands and iron bands are permitted.

(A) is a blue spinel with iron as the main component ,

(B) is a cobalt spinel with cobalt as the main component .

This is a sorting by the Japan-German Gemological Institute. The stone in question is the one on the far right (from Tanzania) of the three cobalt stones shown at the top. The color is due to the cobalt, but it is quite dark. Although it is vivid, the impression changes considerably depending on the shade.

~Products we handle~

GemTreeJapan carries two types of spinel: pure cobalt and cobalt and iron .


This is the comment section of the EGL sorting. There are two types: [Cobalt and Iron Spinel] and [Cobalt Only Spinel].