School of gemmology

How to determine the type of treatment applied to the gems? What is the impact of this modification on the value of the stone? These questions belong to the daily life of the gemologist, that is to say the one who studies natural or treated stones.

It is with the aim of progressing in my job as an appraiser for insurance companies that I enrolled in a gemology school. I passed my gemology diploma in 2008 in a school in Marseille that accepts beginners. This is how I discovered an environment of enthusiasts where the question of sharing knowledge was the very foundation of this young scientific discipline.

5th seminar of the gemology laboratory of Marseille 

Agata Cristol, founder of GEMLAB, passed on the rigor of expertise "not believing what we are sold... we must look closely and prove our analysis by the proper use of scientific measuring instruments".

Given the very high demand for quality gems, in terms of color and purity, sellers quickly adapted to meet these requirements by enhancing the stones with traditional local techniques. What can we know about these "transformation secrets" and how far can they go without denaturing the stone? What do buyers of sapphires, emeralds and purple jade think?

1) Sapphire treatments and their impact on prices by Alexandre Eichler

It is necessary to distinguish the "old burn" from the "new burn"; today's furnaces work with high technology.

For customers, color remains the primary criterion for purchase even if the stone has undergone treatments to improve its intensity, change the color or form a star. While for professionals, the difference between a natural and a "treated" stone (even slightly heated) marks two distinct categories, the final customer seems more sensitive to the color, i.e. to the visual aspect.

2) The Colombian emerald (according to information given at the first international symposium on the Colombian emerald in Bogota) by Laurent Seneca

All emeralds are oiled, so it is hard to believe that an emerald is sold "untreated". As this is a very porous and fractured stone, and knowing that explosives are used to extract them from the rock, it seems impossible not to treat it from the start.
There are non-hardened oils .... such as cedar oil. We can ask ourselves if it is not a mixture with palm oil (more viscous) or synthetic oil in order to reduce costs?

... and hardened resins: such as glue. This type of product was used in an abusive way (at the beginning) we even found emerald powder glued back together!

3 ) Purple jadeite and its imitations by Kate Palthey

There are many colors of jade whose deposits are mainly located at 70% in the north of Burma the rest, is distributed in Guatemala, Japan and Turkey.

It is a metamorphic stone blocked in alluvial deposits and found in the form of pebbles.

Mainly, this stone symbolic for the Chinese since 4700 BC, of which were made buckets for the Emperors, are very sought after in the auction rooms in France since the years 2000.

The distinction between jadeite and nephrite was established in 1863 by Alexis Damour.