Treatments

Treatments are artifical processes that modify the visual appearance of gems. They can improve colour, clarity, transparency or durability. 'Enhancement' can also include re-polishing or extra faceting but 'treatment' is the preferred term.

Scientific advancements have made it possible to modify the appearance of less attractive gem material into visually appealing treasures, making them look like their rare counterparts. Only rarely find mined gemstones with superior colour and clarity and no visible imperfections. Historically sort after by royalty and the wealthy.

There are a range of treatments from producing a small change to drastic processes. Some treatments aren't good for gems making them less durable or giving colour that fades over time. Done to improve commercial potentialy and usability, within the context of a global jewellery mass market that needs gemstone in sufficient quantity and quality to make affordable.

Value of some stones will depend on whether they have been subject to treatment or if the colour/clarity is natural. Many of today's gems receive treatment of some kind. Many gems wouldn't be used in jewellery or would be very expensive if not treated. Therefore full disclosure is important. The CIBJO (World jeweller Confed.) has strict regulations re disclosure down the supply chain. Disclosure is a legal requirement to help preserve customer confidence.

Today most high value gems are submitted to a lab to check for treatments. Lab has equipement, experienced gemmologists, large reference collections of treated stones to compare with (also ensures the nature of treatments are consistently measured and documented).

Techniques to alter colour or clarity - heating, irradiation, dyeing, waxing, bleaching.

For last 200 or so years most stable treatments seen as normal practice. Fewer treatments were available but usually possible for a dealer/jeweller to detect them. Eg: backing coloured gems with coloured foil was accepted until 19th century. Historically gems were also dyed using 'quench-crackling' (still done today) - heat crystal then quench in cold water to create cracks throughout - then immerse in coloured dye to permeate cracks.

Remember - if something look fantastic then suspect an enhancement.

Heating

Used since antiquity to improve colour and clarity and still used today. Heat may enhance value to an otherwise unattractive gem.

Rubies are rare and desirable and often heat treated to improve colour. Vast majority of mined rubies are more translucent than transparent and may be heavily fractured and included. Can contain 'silk' inclusions (fine needles of the mineral rutile) and when stone is heated the silk can dissolve and the stone become more transparent / improves clarity.

Irradiation can be used separately or in combination. Irradiation is generally safe and durable, yet irradiated gemms in USA have to be produced / imported by a company licensed by the Nuclear Regulatory Commission.

Sometimes can combine heat and an additional substance to cause the colour modification eg: Sapphire heated with beryllium where the change will depend on nature of the original material. Some blue sapphire will become more attractive blue, some dark blue or green can become orange.

Heating is a routine procedure with blue aquamarine. Considered and undetermined treatment as science cannot distinguish colour authenticity.

Example where stones differ in colour authenticity but are still natural rubies. Different in nature of colour and market value as the unheated is rarer, therefore more desirable and expensive:

1) uncut ruby crystal from Mogok, Myanmar. Vivid red colour with only a few eye-visible inclusions. Only requires the work of a palidary to turn into a fine cut ruby. A rare find, which when returning from a lab a gem has a label of 'no indication of heating'.

2) uncut ruby crystal from Mong Hse, Myanmar. area know to produce rubies with purpleish to blueish darker cores sometimes with lower clarity caused by profuse fissures. in this case heat treatment will eliminate the blue to purple areas to get a uniform red stone. A procedure done before cutting. Lab report will return stating 'indications of heating (to modify the colour or transparency of the stone)'.

Oil and Resins

Surface fractures can be filled with these to improve overall clarity and colour by decreasing the visibility of fissures. An old process now carried out using sophisticated resins and polymers. Similar methods used in other gems to decrease porosity.

In some cases cracks are deliberatly made in a process called 'crackling', so they can be impregnated with coloured dyes.

Fractured filling of emerald is generally accepted but controversy about ruby filling. Lead glass is used to fill voids in poor quality rubies. A near opaque and purplish ruby is treated before cutting and polishing, produces stones that to the undiscerning eye looks good. On inspection turn out to be several bits of ruby held together with glass. Filler is not stable and can become visible or removed with heat, various basic cleaning methods and household chemicals, lemon juice or vinegar.

Today can impregnated with plastics or wax to improve colour and durability eg: with turquoise, jade,palis lazuli.

Eg: Jade is bleached to remove dark areas, results in porosity which in itself is reduced by impregnation with a polymer, often following dyeing to a required colour.

Coatings

Coat with a thin layer to alter colour. Despite thinness and near transparency, can have spectacular results in otherwise colourless gems, eg: iridescence effect of the 'mystic topaz'.

Some minerals can be coated eg: quartz heated in a vacuum and gold vapour added. Produces a metallic sheen on the surface called 'aqua aura'.

Initially were pigments such as pink on back of diamond. Still used today. Modern coating is often metallic oxides applied to the back of gems.

Examples

• Pliny talked of minerals and gems and how to detect 'false gems'
• carnelian was being improved 4000+ years ago
• record of heating rubies in Ceylon 800 yrs ago
• heat treated Tanzanite turns from brown to blue
• blue topaz subjected to irradiation to deeper colour - an accepted and stable treatment. Most on the market are colourless. Irradiation and heat induces the blue colour
• citrine - much was amethyst that was heat treated to turn yellow
• oiling emeralds to decrease visibility of fissures
• lead glass filled diamond is done to boost clarity. Not stable Has a lower melting point so jeweller needs to know if doing repairs
• coatug on cubic zirconia (CZ)