Gubelin Gemmology

The shape and carat weight of a cut gemstone are usually influenced by the shape of the rough. The crystal habits of rough sapphire can be bipyramidal, prismatic, or tabular. During the cutting process, the cutter needs to select the most appropriate cut according to the characteristics of the rough in order to maximize the gemstone’s weight while achieving the best possible colour.

Furthermore, the proportions and symmetry of the cut are also very important. If the pavilion is cut too shallow, the gemstone may appear colourless in the centre, a phenomenon known as a “window.” Conversely, if the pavilion is cut too deep, the gemstone may appear dark or dull around the edges, a phenomenon known as “extinction.” Therefore, sapphire cutting requires a high level of experience and skill on the part of the cutter.

Photo 1: Prismatic habit with basal terminations
Photo 2: Tabular habit

Would you like to learn more but wonder where to start?

From the comfort of your home, you can join our online “Basics” courses. These courses provide an introduction to the gemmological, practical, and historical fundamentals of ruby, emerald, and sapphire.

Explore our online ‘Basics’ courses (link in bio)

Have you ever seen a gemstone that reminds you of a beautiful stained-glass window in shades of green, red, blue, and violet?
Ammolite is a gem material found in Alberta, Canada. It is formed from the fossilized shells of ancient sea creatures called ammonites, which went extinct 66 million years ago. Ammolite is a delicate and relatively soft material, with a Mohs hardness of 3.5, which means it can be scratched easily. It also has poor stability, meaning that exposure to chemicals, heat, and perfume can cause damage. What makes ammolite so desirable as a gemstone is its magnificent diversity of colour.

Would you like to admire the unique beauty of a gem like ammolite?

Visit our Gübelin Gem Museum, where you can see ammolite for yourself, along with many other fascinating gem materials.

Gübelin Gemstone Museum | Discover the world of gemstones

Photo: Ammolite from Gübelin Gem Museum Wall

The Gübelin Gem Lab and GIA (GIA Education) are delighted to release a joint statement to confirm that Ethiopia is a new source for copper-bearing (paraiba) tourmaline.

Following the rigorous analysis of several hundred reference stones acquired from reliable sources in Ethiopia, the Gübelin Gem Lab has established robust criteria to distinguish Ethiopian material from other known origins. A comprehensive publication in a gemmological journal will be available to read in the coming months.

The Gübelin Gem Lab will now issue Ethiopia as an origin on our reports for any paraiba tourmaline that meets described criteria.

GIA and Gübelin Gem Lab Confirm New Source of Copper-Bearing Tourmaline from Ethiopia - Gübelin Gem Lab For the duration of the fair, the Gübelin Gem Lab (GGL) will offer express on-site testing service for all major gemstones with no express charge.

The Gübelin Gem Lab will provide express on-site testing services for all major gemstones free of express charges at the 74th Bangkok Gems & Jewelry Fair.

Date: 8–12 September 2026

Opening hours: 10:00 a.m. – 6:00 p.m.
(Note: The cut-off time for submitting items at the booth on 11 September is 2:00 p.m. This may be subject to adjustment depending on circumstances.)

Location: Booth No. FD005, Queen Sirikit Convention Center

Booth contact numbers: +66 98 257 1049 or +852
9317 2056

You are welcome to submit your gemstones to benefit from our express testing services. Items submitted by 2:00 p.m. at our booth or 4:00 p.m. at our office (45/1, Soi Silom 19, Silom Road, Silom Sub-district, Bangrak District, Bangkok 10500, Thailand) may be collected in the afternoon two days later.

From 7–11 September, we will also accept goods directly at our Gem Lab (address above) until 4:00 p.m. on 11 September. (Note: This may be adjusted depending on the circumstances.)

Office hours: 9:00 a.m. – 5:00 p.m.
Express service ends on 11 September. Orders submitted on or after 12 September will follow regular testing times.

Please book an appointment in advance by email at [email protected] or call:
Local phone: +66 2 267 5442
Local mobile: +66 98 257 1049

Join Gübelin Academy`s upcoming courses this fall 2026 and be inspired by the incredible world of coloured gemstones.

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

Register at: [email protected]
Gübelin Academy courses also in Hong Kong (Mandarin)

Pearl grading is the process of evaluating a pearl's quality based on a number of characteristics. One of these characteristics is colour.
Pearls occur in a remarkable range of colours. When evaluating pearl colour, Gübelin gemmologists refer to the pearl's body colour and overtones.
The body colour is the pearl's dominant or primary colour. Body colours can range from white, cream, silver, black, and gold to shades of pink, green, blue, brown, and many others.
The overtone is a subtle secondary or modifying colour. Common overtones include pink, green, blue, and purple.
Want to learn more about the beautiful effects light can create in gemstones? Enrol now in our courses and explore the science behind their natural beauty. New dates now open for Fall 2026. Contact us to book your place: [email protected]

10-11 September Level 1 (English) Switzerland
14-18 September Level 2 (English) Switzerland
21-25 September Level 3 (English) Switzerland

29-30 October Level 1 (English) Switzerland
2-6 November Level 2 (English) Switzerland
9-13 November Level 3 (English) Switzerland

Gem aficionados can deepen their knowledge anytime, anywhere with the Gübelin Academy's online course, Coloured Gem Professional: The Basics. Designed for enthusiasts, collectors, jewellery professionals, and connoisseurs, this self-paced course introduces the historical, cultural, and gemmological foundations of the "Big Three"—emerald, ruby, and sapphire—while exploring their beauty, significance, and scientific characteristics. No prior knowledge is required, and each of the four modules can be completed individually. The course fee is CHF 236 (USD 265) and provides the foundation for progressing to Coloured Gem Professional Level 2.
Click the link below to register and begin your journey into the fascinating world of coloured gemstones.

NEXT GEMSTONE TESTING SERVICE WITH CGG IN SHANGHAI, CHINA

We are pleased to announce our upcoming Gemstone Testing Service with CGG in Shanghai, China, and warmly invite you to take advantage of this convenient opportunity to access our services locally.

We will offer free express on-site testing services for all major gemstones at no additional charge.

Event Details
Dates: 12 - 21 August 2026
Opening Hours: 10:00 a.m. - 5:00 p.m.

The event will be conducted in two sessions:
Session 1: Consultation Services

12 - 14 August 2026
During these three days, our gemologists will provide verbal consultations regarding gemstone potential colour or treatment.

Session 2: On-Site Testing Services
17 - 21 August 2026
Comprehensive on-site testing services for all major gemstones will be available throughout this session. Testing will be conducted on-site, and test results will be provided during the event period. Official reports will be issued within 1 to 2 weeks thereafter.

Location:
1st Floor, No. 99 East Beijing Road
Yifeng Galleria
Shanghai 200002, China

Local Mobile: +852 9386 1787
For organizational purposes, we kindly ask that you contact us in advance to arrange an appointment:
Tel: +852 2868 2781
Email: [email protected]

We would also appreciate receiving an estimate of the number of stones you intend to submit for testing.
Should you have any questions, please do not hesitate to contact us.
We look forward to welcoming you and meeting you in Shanghai.