Gubelin Gemmology

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Gubelin Gemmology Gübelin Gem Lab | Gübelin Academy The House of Gübelin operates one of the world’s most respected gemmological laboratories.

In its locations in Lucerne, Hong Kong and New York, the Gübelin Gem Lab provides analyses of coloured gemstones, diamonds and pearls. Its highly esteemed Gemmological Reports are relied upon by famous auction houses, gem traders, collectors, connoisseurs, royal families and others who seek an expert, independent opinion. To share its expertise with the greater public, Gübelin opened the Gübelin Academy. Geared to professionals as well as enthusiasts and connoisseurs of coloured stones, the Academy offers a series of modular programmes providing a unique fast-track training into the wonderful world of coloured gems.

Partially healed fissures can occur in a wide variety of forms. This example was found in an unheated 5 ct sapphire from...
09/10/2026

Partially healed fissures can occur in a wide variety of forms. This example was found in an unheated 5 ct sapphire from Kashmir and is referred to as a “frosted fissure” at Gübelin Gem Lab.

This type of partially healed fissure is particularly characteristic of sapphires from Kashmir, although similar features can also occur in sapphires from other origins.
FOV: 2.8 mm

Photomicrograph: Klaus Schollenbruch, Gübelin Gem Lab, Lucerne
Macro photo: Denise Iwamoto, Gübelin Gem Lab, New York

25/09/2026

You asked, we answer: Part 2. 💙

The conversation around Cornflower Blue continues. In the second part of our Q&A, our Managing Director, Dr. Daniel Nyfeler, answers more of the questions submitted by our community and explores some of the finer details behind this trade colour.

Thank you once again to everyone who shared their questions and joined the conversation. We hope this Q&A brings more clarity to Cornflower Blue and the criteria behind its assessment. 💎

24/09/2026

You asked, we answer.

Following the announcement of Cornflower Blue as a new trade colour offered by Gübelin Gem Lab, we received many thoughtful questions from our community.

In this Q&A, our senior gemmologist, Pierre Hardy address your questions and take a closer look at the criteria behind Cornflower Blue.

Thank you to everyone who joined the conversation and submitted a question. 💎

And there is more to come - stay tuned for Part 2 of our Cornflower Blue Q&A.

Have you ever wondered why gemstones are weighed in carats? And why one carat equals exactly 0.20 grams?The modern metri...
22/09/2026

Have you ever wondered why gemstones are weighed in carats? And why one carat equals exactly 0.20 grams?

The modern metric carat was standardized in 1907 at exactly 200 milligrams, or 0.20 grams. But the origins of the word carat go much further back.

The term is derived from the carob tree (Ceratonia siliqua). In ancient times, carob seeds were used as counterweights on balance scales when weighing precious materials such as gemstones. Their relatively consistent size made them useful for this purpose, although historical carat weights varied from region to region.

Today, one carat is precisely defined as 0.20 grams, and the carat is the standard unit of weight for gemstones.

So, the next time you hear the word carat, remember that its origins can be traced back to something as simple as a tiny carob seed.

Join our Gübelin Academy courses in October and November 2026 and deepen your knowledge with expert instruction.

Upcoming Courses | October/November 2026

29–30 October | Level 1 (English)
2–6 November | Level 2 (English)
9–13 November | Level 3 (English)
16–17 November | Practice Days (English)

To register, contact us at: [email protected]

Photo: Carob Seeds, Gübelin Gem Museum

What turns a pale, milky sapphire into a striking blue gemstone? We take a closer look at Geuda sapphire and the transfo...
18/09/2026

What turns a pale, milky sapphire into a striking blue gemstone? We take a closer look at Geuda sapphire and the transformative effect of heat treatment.

Geuda is a type of corundum, typically found in Sri Lanka’s gem-bearing gravels. It is usually semi-transparent to translucent, with whitish, brownish, milky, or silky appearances. Heat treatment can transform this material into beautiful and marketable gems. For example, Sri Lankan Geuda sapphires can develop striking blue colours when heated, significantly enhancing their beauty and appeal.

While heat treatment can produce beautiful sapphires, a sapphire with a comparable natural colour would generally be more valuable than one whose colour has been enhanced through treatment. This is why treatment disclosure is essential, allowing buyers to understand the gemstone’s characteristics and make informed decisions. Today, the majority of sapphires are heat treated.

Our Level 2 course explores these topics in greater depth, helping you build the knowledge and skills to confidently understand gemstones.
To book your place, get in touch with us at: [email protected]

Next Courses:

Lucerne, Switzerland (English)
10-11 September Level 1
14-18 September Level 2
21-25 September Level 3
28-29 September Practice Days
29-30 October Level 1
2-6 November Level 2
9-13 November Level 3
16-17 November Practice Days

Hong Kong (Mandarin)
10-11 September Level 1
21-25 September Level 2 - fully booked
29-30 September Level 1
5-9 October Level 3
21-22 October Level 1
26-30 October Level 2

Photo: Rough Sapphire from Sri Lanka, Gübelin Gem Museum Wall

16/09/2026

More than a color. A language of excellence. Discover why Gübelin Gem Lab adopted the term Cornflower Blue.

15/09/2026

Cornflower Blue, a term synonymous with exceptional sapphires and now officially adopted by Gübelin Gem Lab from 1 January 2027. More than a colour, it represents a rare combination of characteristics reserved for the finest stones. Discover what defines Cornflower Blue with Dr Daniel Nyfeler.

Cornflower Blue - a new trade colour for GübelinWe are pleased to announce the introduction of Cornflower Blue beginning...
14/09/2026

Cornflower Blue - a new trade colour for Gübelin

We are pleased to announce the introduction of Cornflower Blue beginning January 1st 2027, a trade colour available for Gübelin reports for natural blue sapphires of exceptional colour and visual quality

Inspired by the characteristic blue of the cornflower (Centaurea cyanus), the term cornflower blue has long been used within the gemstone trade, although interpretations of its exact definition vary.

With Cornflower Blue, the Gübelin Gem Lab establishes a stringent and clearly defined set of criteria for this coveted trade colour.

To qualify for Cornflower Blue for Gübelin, a sapphire must meet the following criteria:
• Natural blue sapphire from any geographical origin
• No signs of treatment, including heat or clarity enhancement
• Saturated blue colour with a light to moderate tone, possibly with a gentle hint of violet
• Homogeneous colour distribution
• High level of transparency; a slight velvety appearance caused by subtle light scattering is welcome, though not compulsory
• No eye-visible inclusions and no dark inclusions
• No major windowing or extinction
• Lively colour reflections (when faceted)

The designation Cornflower Blue for Gübelin is independent of geographical origin and is assessed based on the individual visual characteristics and quality of the sapphire. Only a small proportion of blue sapphires are expected to fulfil all required criteria.

From January 2027, qualifying sapphires will be eligible to receive the Cornflower Blue on reports issued by the Gübelin Gem Lab.

Clients who have submitted a sapphire to the Gübelin Gem Lab within the past five years may request a reconsideration of their stone for the Cornflower Blue. For eligible stones, the reconsideration service will be offered at a 75% discount on the applicable service fee.

11/09/2026

What goes into the Gübelin Gemstone Rating?

Behind a single number lies a detailed assessment of the characteristics that make each coloured gemstone unique.
In this Reel, Daniel Nyfeler, Managing Director of Gübelin Gem Lab, introduces the three main components of the rating: Quality, Rarity and Salience.
Quality considers the visual characteristics of the gemstone, including its colour, clarity and transparency, as well as cut and brilliance. Rarity takes into account factors such as gem type, size and treatment. And then there is Salience - capturing the exceptionality and attractiveness that allows a gemstone to truly stand out.
Together, these components contribute to the final Gübelin Gemstone Rating on a scale from 0 to 100 Gübelin Points.
One number, built from many characteristics.

The Gübelin Gem Lab will offer express on-site testing service for all major gemstones with no express charge in Jewelle...
10/09/2026

The Gübelin Gem Lab will offer express on-site testing service for all major gemstones with no express charge in Jewellery & Gem World Hong Kong 2026 .

We are looking forward to meeting you at 3H00, Asia World Expo Hong Kong (AWE). Our opening hours:

14th - 18th Sep, 2026: 10:00 a.m. - 6:00 p.m.
18th Sep, 2026: 10:00 a.m. - 5:00 p.m.

For Hong Kong Convention and Exhibition Centre (HKCEC), our location is 3M209

Our opening hours: 🕔
16th – 20th Sep, 2026: 10:00 a.m. – 6:00 p.m.
20th Sep 2026 : 10:00 a.m. – 5:00 p.m.

You are welcome to submit your gemstones to enjoy our express services. Goods submitted by 2pm at our booth or 5pm at our office in Central, may be collected in late afternoon after two days.

During the fair period, we equally accept goods directly at our Gem Lab in 1004-1005, 10/F., China Building, Central, Hong Kong from Sep 14th until Sep 21st , 2026, office hours in Central are from 9:00am to 6:00pm.
Please book an appointment in advance by email: [email protected] or call:
+ 852- 2868 2781.

We look forward to greeting you in Hong Kong.

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Lucerne

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