Gubelin Gemmology

Emerald clarity enhancement is reversible and repeatable, a reality sometimes misunderstood in the emerald trade.

Unlike many gemstone treatments, the filling of emerald fissures with oils or resins is not permanent. Fillers can be removed, reapplied, or changed over time. As a result, a gemmological report represents only the condition of the stone at the exact moment it was examined in the laboratory.
A stone described as showing “no clarity enhancement” today may not necessarily remain in that condition tomorrow. This is why the Gübelin Gem Lab accompanies reports of such emeralds with an additional Information Sheet, emphasizing the temporary nature of the treatment status.

At Gübelin Gem Lab, we believe that education is essential for protecting collectors, traders, and consumers alike. Understanding the dynamic nature of emerald clarity enhancement is a crucial part of responsible gemstone ownership. A deeper understanding of treatments in emeralds can be gained at Gübelin Academy classes

Gubelin Gem Lab are happy to announce our participation at the Jewellery & Gem ASIA Hong Kong from the 18 th to 21 st of June 2026.

Orders that are submitted by 2 pm at our booth or 5 pm at our office in Central, may then be collected in the afternoon two days later. Please contact us for more details.

During the fair period, we equally accept goods directly at our Gem Lab in 1004-1005, 10/F., China Building, Central, Hong Kong from 16th to 23rd June 2026, office hours in Central are from 9:00am to 6:00pm.

For an appointment with the Gübelin Gem Lab, please email us at [email protected] or call us at +852 2868 2781.

Jeremejevite is among the rarest gem minerals encountered in nature.

Recently, we had the pleasure of testing a particularly attractive example of 17ct.
First discovered in Siberia in the late 19th century, jeremejevite is a borate mineral typically found in small crystals, with facetable gem-quality material being exceptionally scarce. Its delicate blue to colorless hues and remarkable transparency make fine specimens highly sought after by collectors and connoisseurs alike.
Because of its rarity, every gemmological examination of jeremejevite offers a fascinating glimpse into one of the more unusual corners of the gemstone world.

Photo: Riwin Lertsinathichai, Gübelin Gem Lab, Bangkok

With kind permission of Zam Refai, Zam Gems (Pvt) Ltd. Zam Gems

Do you appreciate organic materials in jewellery?

Coral is a beautiful material with an organic origin. Coral is actually formed from the skeletons of marine animals called polyps. Calcium carbonate is deposited in the form of branch-like structures. Through a biomineralisation process, a microcrystalline material known as coral is formed. Under close observation, one sees that coral has a pitted surface with parallel markings. Once it is polished, its lustre is vitreous, just like the lustre of the majority of crystalline gem materials.
If you are interested in seeing a variety of gem materials, come visit the Gem Wall at the Gübelin Gem Museum, where you can explore a variety of organic, inorganic, natural, and synthetic gem materials.
Gübelin Gem Museum in Lucerne, where every stone tells a tale and every detail is a clue waiting to be uncovered.
Featured here is a beautiful 7.23 ct polished free form coral from our Museum Gem Wall.
Opening hours: Wednesday, 9:00–17:00
Private Guided tours: By appointment

Book your ticket using link in bio

Quo vadis?
Rutile “arrowheads” in this sapphire point in multiple directions, creating a visually intriguing and somewhat disorienting internal landscape. Yet, while their orientation may seem ambiguous, the combined evidence from inclusions, spectroscopy and chemical analysis clearly identifies this gemstone as an unheated sapphire from Sri Lanka.
Photomicrograph: Klaus Schollenbruch, Gübelin Gem Lab, Lucerne
Photo: Supreeya Mukpimai, Gübelin Gem Lab, Bangkok

In our Level 2 Coloured Gem Professional course, we learn what an orogeny is and how orogenies are related to gemstone formation. Tanzanite formed approximately 550 million years ago during the Pan-African orogeny. Tanzania is the only source of this unique gem.

Also in Level 2, we explore the marvels of gemstones and how they interact with light. In this case, Tanzanite exhibits trichroism, displaying different colours along its three crystallographic axes.
We invite you to explore our courses and be empowered in the trade through knowledge. Register now for September courses.

To register, contact us at: [email protected]

Very large gemstones often present particular challenges when it comes to photomicrography. Yet this aquamarine, weighing over 700 carats, revealed an inclusion well worth the effort. A broad network of thin films is intersected by clouds of minute channels, creating the impression of moth-like internal structure defined by the interaction of thin films and densely distributed micro-channels.

Photomicrograph: Klaus Schollenbruch, Gübelin Gem Lab, Lucerne
Photo: Fashiel Tamimi Yanos, Gübelin Gem Lab, HongKong

Can you guess an emerald’s origin from its inclusion scenery?

Origin determination is far more complex than it may seem. While microscopy is an essential tool in gemmology, origin should never be determined based on microscopic features alone. Advanced analytical methods play a critical role in reaching a reliable conclusion.

That said, inclusions can offer remarkably helpful clues. Certain features can point us in the right direction and help narrow down possibilities.

It’s a fascinating challenge for gem lovers and professionals alike. Take a close look… what’s your guess?

Image 1: Three-phase inclusions with jagged outlines in an emerald from ?
Image 2: Mica (biotite) platelets, growth tubes and blocky two-phase
inclusions in an emerald from ?
Image 3: Blocky two-phase inclusions in an emerald from ?
Image 4: Iridescent thin films in an emerald from ?

Want to better understand these inclusion scenarios and how they relate to origin? Join our Coloured Gem Professional courses now!

Photomicrography Workshop
Keen on learning how to take your own pictures of the inner world of gemstones?

Immerse yourself in the captivating world of gemstone photomicrography. Next month the Gübelin Academy hosts its workshop on the photomicrography of gemstones. In this 2-day hands-on workshop we will guide you through the art of capturing the mesmerizing beauty hidden within gemstones. You will learn techniques for photographing gemstone inclusions using a microscope, revealing the breathtaking, often unseen details that lie beneath the surface.

Designed for gemstone lovers of all levels, whether you’re just starting out or already have experience, this workshop offers something for everyone. Don't miss this unique opportunity to explore and capture the inner world of gemstones!

Photomicrography of Gemstones Workshop
Date: 29-30 June 2026
Duration: 2-day workshop
Price : CHF 1,390
Location: Gübelin Gem Museum, Lucerne
Language: English
Prerequisites : Students are asked to bring their own laptop or tablet

Just a Fissure
Even a simple fracture can reveal unexpected beauty. This fissure in a spinel from Tajikistan displays a striking sequence of colours that differs from the familiar rainbow spectrum. Instead of following the typical order produced by dispersion, the colours transition from colourless through yellow, orange, red and violet-blue, returning again to yellow—while green remains notably absent. This unusual palette is the result of thin film interference, rather than refraction and dispersion.

Photomicrograph: Klaus Schollenbruch, Gübelin Gem Lab, Lucerne
Photo: Larissa Frank, Gübelin Gem Lab, Lucerne