Gem-A英國台灣校友會

04/08/2026

21/07/2026

A type IIa diamond exhibiting atypical phosphorescence 💎

Recently, NGTC's Shenzhen Laboratory examined an approximately 1 ct, E-colour, type IIa diamond that exhibited unusual phosphorescence.

When examined with a SYNTHDetect unit, the stone showed weak blue fluorescence and phosphorescence, while the DiamondView caused violet-blue phosphorescence.

While phosphorescence is extremely rare in natural type IIa diamonds—potentially arising from trace amounts of boron undetected by infrared (IR) spectroscopy—its presence in type IIb diamonds typically manifests as chalky blue-green, or in rare instances, red phosphorescence.

The phosphorescence spectrum of the diamond obtained with a GEM-3000 unit revealed a previously unreported peak at approximately 378 nm and, after performing peak deconvolution (or spectrum resolution), another peak at 413 nm.

📸 The approximately 1 ct pear-shaped diamond showed blue fluorescence in the SYNTHDetect unit. Photo by W. Zhu.

📚 Gem-A Members can read more in the latest Journal of Gemmology (Volume 40, No. 2, 2026): https://gem-a.com/publications/the-journal-of-gemmology/volume-40-issue-2-2026/

Become a Gem-A Member to start receiving our magazines and other benefits: https://gem-a.com/membership/

02/07/2026

Iridescent andradite from Niger 🤩

Iridescent (or 'rainbow') andradite is one of the more obscure and unusual garnets and is known in gem quality from only a few localities, such as Nevada and New Mexico in the USA, Sonora in Mexico, and Tenkawa in Japan.

The origin of the colourful iridescence has been attributed to thin-film interference from complex lamellar structures in the garnet.

A relatively new and unknown source of iridescent andradite is Niger in West Africa. The material occurs in skarn veins about 150 km from the Tchibarakaten goldfield in the Arlit Department of the Agadez Region, near the southern edge of the Sahara Desert, close to the Algerian border.

The remoteness of the locality and the informal nature of mining have limited proper study of the occurrence, and the exact host rocks and formation sequence of the iridescent garnet have not yet been documented.

📸 This view of a 2.20 ct iridescent andradite from Niger shows areas of strong iridescent colour, along with a pit in one of the lightly polished crystal faces. Photo by Bear Williams.

📚 Gem-A Members can read more in the latest edition of The Journal of Gemmology (Volume 40, No. 2, 2026): https://gem-a.com/publications/the-journal-of-gemmology/volume-40-issue-2-2026/

Would you like to start receiving our magazines? Consider becoming a Gem-A Member or Associate Member today: https://gem-a.com/membership/

30/06/2026

什麼是四大寶石？

What are the ‘Cardinal Gems’? 🧐

As Pat Daly FGA DGA explains on the Gem Hub, this term can be used to spotlight five gemstones – diamond, ruby, sapphire, emerald and amethyst – on the grounds that they had special significance, preciousness and value in classical Roman, Greek, Egyptian and Mesopotamian cultures.

Read more on the Gem-A Gem Hub: https://gem-a.com/gem-hub/gem-knowledge-what-are-the-cardinal-gems/

Are you ready to start your gemmology journey?

💻 Learn online, in your own time and at your own pace with GemIntro: https://gemintro.gem-a.com/

11/06/2026

Could you be the freelance gemmology tutor we are looking for? 🧐

We are recruiting for a new external assistant gemmology tutor (visiting tutor) to teach evening classes at Gem-A London on a freelance basis.

It is essential that you have a Gem-A Gemmology Diploma and the ability to commit to teaching two nights per week (Mondays and Tuesdays) from September 2026 until July 2027.

The right candidate will have the opportunity to progress to become a lead tutor after training.

Read the complete job description and requirements here: https://gem-a.com/about/careers/external-assistant-gemmology-tutor-visiting-tutor/