Precious and Semi-Precious Stones. Part B: Gemstone Treatments and Enhancements

Treatments and Enhancements: Most gemstones in the affordable range have been treated in some fashion.  A reputable dealer or jeweller should be able to tell you how the gemstones they use have been treated, whether it's heat, colouring, stabilisation, irradiation or whatever.  I tell my suppliers that it doesn't matter what the treatment is, so long as I know about it.  Then I can tell my clients and THEY can make up their minds whether to buy or not. 

Certificate of authenticity for a sapphire, and a collection of mixed stones 


Treatments for diamonds is not all that common. High temperature and high pressure (HPHT) is an effective tool for changing the color of certain diamonds, making them colorless, pink, blue, green, yellowish green, or yellow. This form of diamond treatment is virtually undetectable.

Diamonds showing fractures


Fracture filling is occasionally used to hide small fractures in a stone. A glass-like substance is injected into the fracture to make it less visible and to improve the stone’s apparent clarity.

Rubies are commonly heat treated to enhance their colour. Temperatures in excess of 1700 degrees Celcius are used with sometimes dramatic results. By undergoing a heat treatment, a ruby gets better color clarity and intensity. This treatment also removes or reduces the inclusions that a ruby gem may contain.

Another set of treatment that a ruby gemstone may go through include flux-healed treatment which is an extreme heat treatment. In this treatment, flux like material is induced in ruby which is then molten at very high temperatures. Once dissolved, this flux is then used to fill the fractures and cavities that are there in the gem and solidify it into a glass-like substance. This treatment helps in improving the clarity of the gem.

Rough (uncut) rubies

Various shapes of cut rubies

Most commercial Sapphires have undergone some level of treatment.  Most have been heat treated to enhance the colour, while some are also filled (see treatment for rubies). A non-heated stone of good colour is likely to be more expensive than a heated one.


 Fancy coloured sapphires bought on my last trip to Thailand

Rough multi-coloured sapphires


Some sapphires are also treated with titanium or beryllium to enhance colour.  Titanium develops a more intense blue, while beryllium produces rich oranges and yellows.


Trays full of treated sapphires in Bangkok


It would be fair to say that most emeralds have undergone treatment of some kind.  The stones naturally have small fissures which are usually oil treated. A large amount of emeralds on the market have inclusions, so one without any inclusions is rare.  Heat treatment is never used on emeralds.


Some beautiful emeralds. The one in the ring shows inclusions


Semi-precious stones are equally fascinating and generally a whole lot more affordable.The range of colours, shapes and possibilities are limitless.

I have a great fondness for aquamarines, amethysts and peridots, which I use in a lot of my jewellery.  My preference is for rough-cut stones, which show the character of the stone.


Me marking up rough aquamarine in India


My obsession with Aquamarines has translated into many pieces of jewellery


I've recently discovered the range of colours in tourmaline from pink to deep green.  Tourmaline also appears in a black form as well as a yellowish colour.  'Watermelon' tourmaline has a centre of pink with a green circumference.  I'm still working out how to use this effect.

'Watermelon' tourmaline


Garnets come in a wide variety of colours, from the brilliant deep orange of Hessonite to the vivid green of Tsavorite, via all the orangy-reds, reds and purplish reds that we are all familiar with.  


 Three orange hessonite garnets (L) and a brilliant green tsavorite (R)


Most of these semi-precious stones are a considerably cheaper alternative to using precious stones in many instances, although there are some quite inexpensive precious stones out there if you know where to look and what to look for.

There is a world of information out there about gemstones.  If you're interested, go have a look and read up.  They are an absorbing study that could take a lifetime.

And if you'd like something to read about the history of gemstones in a deft mix of history, interviews and travel, try Victoria Finlay's 'Jewels' - Random House.  I loved it.  It's a book you can dip into or read the whole way though.  I keep going back to it. From The Sunday Telegraph (London) 'Throughout history precious stones have inspired passions and poetry, quests and curses, sacred writings and unsacred actions. In this scintillating book, journalist Victoria Finlay leads the reader on a treasure huntfor some of the most valuable, glamorous and mysterious substances on earth. Wiuth intense curiosity and narrative flair, Finlay tells dazzling stories with a wonderment and brilliance truly worthy of her subject'

Got questions about these stones??  Ask me and if I don't know, I'll find out.