GEMSTONE TREATMENTS

Unacceptable and must be disclosed

COATED TOPAZ

Recently the Australian Market has been inundated with pink and other unusual coloured Topaz. Generally this material is colourless Topaz thinly coated with metallic oxides that produce a range of colours including pink and a bluish purple named “Mystic” Topaz. This coating can be easily scratched or polished off.

Natural Pink Topaz is extremely rare and is generally found in small crystals i.e. under 1ct. If you are presented with large stones or a suite of matching stones, it is most likely to be coated Topaz.

Detection is possible. The coating is produced by a “sputtering” method that leaves a “dot-like” appearance on the surface that is visible under magnification. Stones are generally poorly polished and chips or scratches will reveal the presence of the coating. The surface can also show a “metallic” lustre. This treatment must be disclosed to the customer and explained that the colour is not natural and may not be permanent if worn roughly.

BERYLLIUM TREATMENT

When Chrysoberyl was accidentally heated with Sapphire it was discovered that Sapphire colours were altered by the release of beryllium from the Chrysoberyl into the Sapphire lattice. Beryllium is now commonly added through a treatment process to produce yellow, Padparadscha and orange Sapphire and improve the appearance of inferior coloured Rubies. This treatment must be disclosed as the colour is a result of introducing elements into the crystal lattice as opposed to the traditional heating process. Prices of beryllium treated gems are considerably lower than non-treated gems.

Beryllium Treated Gemstone

Beryllium Treated Gemstone

Beryllium Gemstone

Beryllium Treated Ruby Immersed

Beryllium Gemstone

Beryllium Treated Padparadscha Sapphire

Beryllium Gemstone

Beryllium Treated Yellow Sapphire

GLASS SURFACE FILLED RUBY

Pits or holes on the gem’s surface are filled with lead glass instead of polishing them out and reducing the size of the Ruby. Careful examination with a hand lens will reveal a lustre difference between the Ruby and glass filling and bubbles may be visible in the glass filling.

 

Glass Surfaced Ruby
Glass Surfaced Ruby

GLASS FRACTURE FILLED RUBY

Although glass fracture filled Ruby has been on the market for quite a few years it is still being confused with natural Ruby. It is often seen in larger faceted gems and cabochons which are rare in natural Ruby, also in matched sets and cheaper imported jewellery. It is important that jewellers recognise these stones as they are easily destroyed during many basic workshop procedures.

At a glance it appears to look like included Burmese Ruby but on closer inspection heavy twinning and growth striations with a tiny network of fractures breaking the surface of the stone are obvious. These fractures allow the glass to enter the gem and mask the fractures.

Trapped gas bubbles are visible in the glass filling in conjunction with natural inclusions and may be observed with a hand lens or microscope. A bluish haze in the body colour of the stone will be noticeable in strong white light (eg. fibre optic). This is very poor quality Ruby virtually held together by the glass and has little commercial value.

Glass Fracture Ruby
Glass Fracture Ruby
Glass Fracture Ruby

GLASS FRACTURE FILLED SAPPHIRE

The glass-fracture filling of poor quality Ruby has spawned a new treatment, cobalt –glass fracture filling of rejection quality sapphire.

Whereas the Ruby relied on colourless-yellow glass being injected into the multitude of surface reaching fractures, this treatment involves the use of a cobalt-doped (blue) glass, thereby not only improving the clarity of the material but the colour as well.

As with the glass fracture filled Ruby, detection by hand lens will reveal numerous bubbles trapped in the glass and a myriad of surface reaching fractures that appear as scratches on the surface. However, the Sapphire will show intense blue colouration within the fractures, with an appearance similar to dyed crackled quartz.

Glass filled sapphire
Glass filled sapphire

SURFACE DIFFUSION

Is a process where a thin surface layer of synthetic blue Sapphire is diffused into the surface of a poor quality Sapphire to improve the colour and in some cases create a star. This coating can be easily polished off and can be damaged and scratched during everyday wear and tear or whilst being repaired by Jewellers. So while they are cheap, they are not durable. Any sale or purchase of these stones should be accompanied by a full disclosure of the treatment.

When faceted gems are immersed in water against a white background the facet edges appear darker. This is due to the concentration of colour occurring at the junctions of the facets.

Diffusion coating

Surface Diffused Sapphire

diffusion coating sapphire

Surface Diffused Sapphire Immersed

diffusion coating sapphire

Surface Diffused Star Sapphire

When illuminated from behind, the poor quality green/blue sapphire disguised by this diffused star is revealed.

diffusion coating sapphire