Authentication of small diamonds
Since 2004, the Swiss Gemmological Institute – SSEF checks the authentication and the quality of colourless small diamonds (melee) batches for many luxury watchmaking and jewellery manufacturers in Switzerland abroad.
ASDI – Automated Spectral Diamond Inspection is a highly specialised instrument developed by SSEF that enables the screening of melees at a high speed and reasonable price.
Quality control of small diamonds
The Swiss Gemmological Institute SSEF has set up a strict protocol for the quality control of colourless small diamonds (melees and baguettes), fitting with specific requirements of the watch- and jewellery industry. The detailed information available on SSEF reports help our clients to evaluate the quality of their lots of small diamonds and maintain their quality management. Our routine ensures the best reproducibility of results and provides our clients results they can trust.
We routinely control colour, clarity and cut quality of small diamonds. Each diamond that is subject to quality control is also authenticated using the ASDI instrument, with the aim of sorting out any and every synthetic diamond or diamond imitation.
- Each small diamond is placed table down in a white folded paper under a normalised light.
- Each small diamond is compared to our CIBJO diamond Masterstones.
- When checking the colour of a small diamond it is important to compare it to a large diamond masterstone. This reduces colour grading margin errors, as opposed to the comparison with a small diamond masterstone.
- A sortoscope microscope is used for the clarity control of small diamonds and enables the visual control of a large quantity of small diamonds.
- The size of an inclusion may be measured with a special eyepiece.
- Stones may be compared with SSEF clarity master stones.
- The final purity grade is defined by means of the 10x loupe.
Cut (symmetry, polish, proportions)
- SSEF has created a Symmetry Masterset for small diamonds. This Symmetry Masterset groups more than 30 selected diamonds from an ‘Excellent’ to a ‘Poor’ symmetry grade.
- For evaluating the symmetry grade of a diamond we check : roundness ; eccentric or tilted or wavy tables, truncated or short facets, facets of unequal size, edge displacement ; girdle with unequal thicknesses, etc.
- SSEF has created a Polish Masterset for small diamonds. It groups more than 8 selected diamonds from «Excellent» to «Poor» polish grade.
Pricing for quality control of melees: sampling basis (English and French) or 100% quality control (English and French)
Sample reports for a batch of small diamonds may be found here in French: full lot tested (PDF) or random sampling (PDF)
*Please also note the terms & conditions for submission for quality control of small diamonds in French (PDF)
Explore our research library
ISO standards in the diamond trade: history and benefits
Presentation at the 2022 Rendez-Vous Gemmologiques de Paris Conference by Jean-Pierre Chalain (original version of this presentation was in French, this version has been translated into English)
Diamond fraud uncovered
As in the past, the SSEF is regularly asked by the Swiss police authorities to act as a gemmological adviser in criminal cases. Usually, these are fraud cases, involving undeclared or mislabeled gemstones or their imitations. In a recent case with about 20 stones submitted by the police, we not only
A new led daylight source for diamond colour grading
In 2020, a novel light source for the colour grading of diamonds was developed in a collaboration between SSEF and the Department of Physics, University of Basel (see Figure 1). In contrast to many of the models on the market, the new light source uses state-of-the-art LED (Light Emitting Diode) lig
Two exceptional asteriated diamonds
by Dr. L. Speich & J.-P. Chalain, first published in Facette 27 (June 2021) Recently, SSEF received two so-called asteriated diamonds for authentication. Asteriated diamonds are rare and highly prized amongst collectors for their beautiful and unique appearance. The two stones received
Diamonds as a window into the earth
by Dr. L. Speich, first published in Facette 26 (May 2020) Diamond is valuable as a gemstone but it is also a mantle geologist’s best friend because it provides a rare opportunity to study processes that occur deep in the Earth. Most diamonds form in the so-called lithospheric mantle within a
Why is a Diamond of Type IIb blue to greyish blue?
Comparing the absorption spectra of type IIa and type IIb diamonds greatly helps to better understand why a diamond of type IIb is blue to greyish blue.
ASDI (Automated Spectral Diamond Inspection)
by J.-P. Chalain, first published in Facette 21 (February 2014) In 2013, numerous trade-press articles and gemmological laboratory alerts warned the diamond industry about the presence of synthetic diamonds mixed together with, or presented as, natural diamonds. These announcements pointed out
Undisclosed natural diamonds mixed in a parcel of synthetic diamond
by J.-P. Chalain, first published in Facette 22 (February 2016) In 2016, our Diamond Department acquired a parcel of small colourless synthetic diamonds produced in Europe by the HPHT method. The complete study of these series of melee size synthetic diamonds (SSEF Research project 80602) is pa
CVD Synthetic Diamonds and Testing at SSEF
by J.-P. Chalain, first published in Facette 20 (January 2013) Synthetic diamonds have been present in the gem trade for over two decades. Recent financial investments and advances in technology have now made them more affordable both in terms of price and availability. The SSEF has been following
The Detection of HPHT-treatment of Diamonds at SSEF: 20 Years later
In 2000, SSEF announced that it was able to identify the HPHT treatment of type II diamonds. About 20 years later, this article summarizes how we were able to achieve this breakthrough and which people from the trade and other research institutions were involved in this important step.
How Diamonds Salted Inside Batches of Synthetic Diamonds Creates Confusion
The diamond trade today is seriously concerned about synthetic diamonds mixed in with parcels of natural diamonds; however, we also propose here that the opposite situation of natural diamonds mixed in with batches of synthetic diamonds is also something to be concerned about and will in the near f
Study of a recut HPHT synthetic diamond: Colour VS size VS SWUV transmission (2019)
Presentation by Jean-Pierre Chalain at the International Gemmological Conference (IGC) in August 2019.