Following on from our last blog about emerald treatments, in this piece I will be having a brief look at synthetic emeralds. There are two main methods of producing man made emeralds which are explained below. I have also looked at how these synthetic gemstones can be detected.
Flux melt growth
A flux is a substance that, when molten, will dissolve another substance that has a higher melting point. The individual components of emerald are melted into a flux. The resulting mixture cannot stay in solution and so crystallises out to form emerald. Flux melt synthetic emerald has a slightly lower refractive index (RI) than genuine emerald. The RI of a material measures the degree to which light is ‘bent’ as it passes through. Flux melt emeralds can also have tell tale inclusions. The solidified flux can create wispy, veil like shapes composed of extremely fine drops. Sometimes small platinum crystal platelets can be present. These are part of the platinum crucible in which the whole mixture was originally heated.
This method imitates the way many minerals crystallize in nature from water solutions at high temperature and pressure. The necessary raw materials are enclosed in a sealed metal container of water called an autoclave. The autoclave is heated until the temperature surpasses the level at which water boils and the steam, which cannot escape, builds the pressure. At around 200°c, the water exists as a dense fluid capable of dissolving materials that, under normal circumstances, are insoluble. Emeralds synthesized in this manner have few inclusions but may have spiky, nail like inclusions and can be highly fluorescent under UV light. They can also display a zig-zag growth structure that looks similar to a heat haze.
If you have any emeralds that you wish to have valued then please contact Simon Rufus of Grand Auctions, Folkestone, Kent.
- Posted by Simon Rufus