Aquamarine and Tanzanite

Discussion in 'Jewellery & Gems' started by BenKenobi, Oct 18, 2017.

  1. BenKenobi

    BenKenobi Active Member

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    I really don't know if there is a business that does it, as far as I know the Sapphire material being produced is export to asia and they handle the process over there. I have tried with Aquamarine but not Tanzanite. There is a right and wrong way, you cannot simply bung your gems in an oven.
    The methods I have read use a slow incremental process to attain the critical temperature then slowly drop, they use a material used in investment casting to cover the gem and provide an even temperature or thermal shock fractures the gem. Some I have read cut the gems then heat, some just the rough, either way due to microscopic particles or inclusions in a crystal structure, heating is a risk, the differing material or gases, or sometimes liquid expands at a different rate. I guess the lower temperature the better, pretty sure Aquamarine and Tanzanite are low temperature as in around 400 c.
     
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  2. BenKenobi

    BenKenobi Active Member

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    A little more info for those interested.

    Aquamarine: Green/Blue-Green Beryl heated in open atmosphere to approx. 450 c, will change the blue-green tones to blue.

    Zoisite (Tanzanite): An interesting material and is found in a variety of colours, the commercially named Tanzanite(blue/purple) if not Blue when mined is usually brown in colour, nearly all Tanzanite sold has been heat treated, most commonly the gem is cut BEFORE heat treatment to rid the gem of any flaws visible. Natural Blue Tanzanite which is unheated displays the strong pleochroic colours brown/green/purple/blue, after heating these qualities are largely diminished and the usual blue/purple colours are attained. The material is heated to around 370 c in open air.(From my personal contact with traders of gem rough, I have been told when buying untreated rough Zoisite the darker the colour brown of the material generally the stronger and more intense the finished blue colour will be after treatment)

    I personally have done heat treatment as an experiment with success on Aquamarine, generally speaking the deeper the tone of green will give a stronger finished blue colour. I have a small electric Kiln I use for investment casting. The temperature is slowly increased of a matter of hours and then reduced likewise. Heat treatment is irreversible. I will say I personally prefer the natural blue/green untreated colour of Aquamarine.

    A word of caution regarding incipient fractures and inclusions of all types in all gems headed for heat treatment, these will naturally expand as the material is heated, even if the material is flawless to the eye there is no guarantee with heating the gem material will not fracture due to microscopic inclusions unseen to the eye, incipient fractures will open further, any other mineral inclusions can produce further fractures due to different density and expansion rates, similarly liquid/gas bubble inclusions will obviously expand also with the same result.
    There are exceptions to this inclusion rule with some gem types typically Corundum, the corundum is heated to around 1600 c - 1900 c depending on the desired outcome necessary in a reducing or open atmosphere for extended periods, this process is used on darker coloured material like the Australian Blue with the object of both lightening the colour and may reduce colour banding also gems with rutile inclusions may also be clarified but a more rapid cooling rate is utilised to prevent re-crystallization of the rutile, how this is done without fracturing I do not know.
     
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  3. silversearcher

    silversearcher Active Member Silver Stacker

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    Thanks for this write up on heat treatment Ben....For those who enjoy cutting gems it's a interesting subject. I believe that many gems are placed in a insulating material within the kiln (plaster of paris) and is set on a timer to slowly heat the gem over a long cycle and slowly cool down to avoid heat shock. Personally, I like the diesel trichroic colours of Tanzanite as is. With the 3 different flashes of colour in it's natural state makes it quite appealing. It's a shame that Australia doesn't have it's own gem industry. I really do not accept the excuse that wages are too high here, hence such a industries are based oversea's. I say this as yesterday I viewed a blue oval cut sapphire set in a in a ring worth $4200 and the girdle was thick and finished off with a 600 grit lap. Really for that money the girdle should be near perfect. It's hard to justify such prices when you see poor work. There must be massive mark ups in the gem industry, but on the flip side people don't appreciate the time and effort that gets put into cutting a gem at a high standard. And there is no doubt that Australian Gem Cutters put a lot effort and time to cut a gem as best as they can. While overseas, it's all mass produced and just churn out as many gems as you can. Cutting gems is a real art form.
     
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  4. BenKenobi

    BenKenobi Active Member

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    Very True silversearcher, in my experience so far and my involvement in the gem and jewellery industries, the mark up are often 400% or by far more, commercial cutting has improved over the years depending on the cutting centre but is no match for custom cutting at the levels we are involved with. Australian market has been impossible to crack as the general public is so uneducated regarding the industry, with the one exception being diamond where a perfect cut and polish demands premiums. Stupid thing is some coloured gems are so much rarer than the diamond. The American market is different due to the population and headway has been made by custom cutters, there is a customer base due to numbers that will pay instead of buying a machine cut synthetic from zamels or commercial cut native gem. Ha I have to laugh, even the diamond grade used at chain jewellery stores is BELOW commercial white standard for diamond- junk in other words and people are more than willing to fork out their cash for it. I have thought of writing a book on Australias jewellery trade, but I may be somewhat over popular for doing so. But the public is simply being completely ripped off to the tune of tens of millions every year from chain stores.
    Australian gem trade does exist but commercial viable grade for cutting seem to be rare, its a fact that many of the coloured gems you see will never be marketed with the Australian name with the exception of diamond and opal, even the Australian sapphires are sold to the Asian market, treated and sold with parcels of gems from other countries where the name denotes a quality standard, eg Ceylon, Sri Lanka etc, this is due to the fact that Australian Sapphire is too dark by quantity and quality, is then heat treated or infused according to the necessary outcome wanted and resold as something else altogether. Australia has quantity in Sapphire and that's what the Asian dealers want as the cost of treatment is nothing compared with the end products value. Even Australian emerald is sold commercially as from another origin, I am not aware of any emerald now being produced from Australian mines commercially.
    In my geological experience with gem prospecting over here in W.A. there is very little that is of gem grade for the precious gem market, I believe it does indeed exist but there are too many factors economically which are preventing further exploration, other gems in other countries are far more economic to mine in comparison. Another factor is our geological weathering profile, there has been literally kilometres of height weathered away by erosion in its various forms from our geological profile in Australia, the gem deposits may well be long gone, weathered away into sand and dust. Some geologists are saying that Australia is the oldest continent on the planet not Africa.

    With heat treatment I have used cristobalite, which is the silica compound used for investment casting(lost wax), used dry and for low temperature insulation.
     
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  5. redhawk5796

    redhawk5796 Member

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    I wish all the jewellers and gemstone traders in Australia are as passionate, honest and fair like both of you. I am sure they do exist, but as someone who is out side the field, I am unsure where to locate them.

    I purchased three 0.65ct-0.68ct pink sapphires from Thailand, which I think need to be re-cut to enhance their brilliance. Went to a jeweller in Melbourne to have 2 stones assessed at $25 per stone. It was just a verbal valuation without certificate which I was well aware of before I proceeded. The info I obtained was they look like they are sapphires and not glassed filled. I did check with him whether he thinks the stones need to be re-cut and his answer was no. He also said that he can help me set them into jewellery, but I am not sure whether he just wants to proceed straight away to jewellery making without making sure I get the best value out of custom made jewellery. I bought the stone for less than AUD 100 each and am not sure whether it is worthwhile to spend $1500 to make them into a ring.

    I will post a photo of the stones when I have figured out how to do so.

    I fully support your idea of writing a book about the gemstone trade in Australia Ben. Let us know if you do so.
     
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  6. BenKenobi

    BenKenobi Active Member

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    to be honest Redhawk, the jewellery trade revolves to an extent on the emotive drive and sentimentality of the consumer. You have to carefully balance what you are planning as your money spent is really nothing more than exactly that, the jewellers work will always be a fairly big bill and make a large percentage of the total cost unless they are also supplying a large diamond or other coloured gem and also because they sell gold with unobtanium prices. The average female ring weighs in at around 3-4 grams and that's a solid band but will retail around 4-8 grand usually more depending on the gems used, I am not talking chain store stuff in this case.
    Investment grade jewellery is another ballgame altogether, where tens of thousands of dollars are spent on a single coloured gem of collector grade quality, which does offset the cost of setting into a custom designed piece along with some nice white or coloured diamonds. The high end handcrafting jewellers are in this category eg Hardy Bros, Charles Edwards. Then there are the deceivers who have a flashy shop, rely on marketing and name, use cast jewellery made by a cad machine doing digital printouts on 3d, and still charge handcrafting prices, one of these as an example is Ninas, there are hundreds like them. They can set a 10 carat Citrine into a 18k w/g band printed and cast by machine whack a few 10 point diamonds in the setting and in the shop window for 8 grand, and some flunky tourist with cash on hand will fork it out on a whim. Beats the hell out of me why you would pay that for quartz and a name but that is how the trade works, its all about market perception and the emotive drive of the buyer that must have.
    The gold alloy is worth nothing more than its weight as scrap karat, unless the gem is outstanding, really a rings valuation tells a story, but in the real world resale is often a third the value realised upon sale if you are able to find a buyer. Your reasons for having a custom made piece must be delineated. Herein are some of the reasons I got into the trade in the first place, I simply decided to keep my money and do it myself, decades later I have all the knowledge and skill I need along with the equipment, I have a jeweller that does my gem setting for me but I supply the gems, I source the rough and cut myself and ring after making the blank into whatever design I choose, if I want any diamond I can get them at wholesale prices and for accent stones its a pittance, this is how you make jewellery and profit from it. It takes decades to get there, now that I am here I suffer from really bad osteo in my fingers and the dexterity needed for some of the work is simply too painful to abide, old(44) bugger I am.
    I probably do not exploit the opportunity and my knowledge, I have a fulltime job that demands my attention otherwise. More than happy to shed some light on the dark secrets of the trade though.
     
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  7. redhawk5796

    redhawk5796 Member

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    Thank you for sharing your knowledge Ben.

    If I remember it correctly, I was told $1500 - $2000 (comes with some small diamonds). I was trying to buy a piece of jewellery to commemorate an event, but was shunned away by the price. Michael Hill is affordable, but the quality isn't great. Most of their diamonds are of poor quality, hence the lower price. I guess I am also paying for the rent of their shop in Melbourne CBD and the salary of their staff. I have not buy any expensive jewellery before, so I can't judge whether the price is fair.

    Do you know any jeweller in Melbourne you can recommend to me?

    I really admire you for the hard work you put in and love all the stones you have posted in this forum. 44 is still very young! That would mean that you started gem cutting in your twenties when everyone is wasting their life with other stuff? You have my respect!

    Oh no, I hope the doctor can do something about your fingers. Are you taking anti-inflammatory medication? You can also have anti-inflammatory medication injected into your joints with an aid of ultrasound. I have osteoarthritis in one of my big toe joints too, so I know it sucks when the pain kicks in.
     
  8. BenKenobi

    BenKenobi Active Member

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    Anti inflammatories are a no no for me due to anaphylaxis, my body is certainly giving me a hard time about, I will check around for a shop in Melbourne but it will take me some time to get back to you on that. Started gem cutting in late teens, while prospecting gold and gems, then in early 20's moved into gemmology, it was only after that in mid 20's I started casting then got more involved in jewellery. Had some early life dramas but am still here to tell of it
     
  9. redhawk5796

    redhawk5796 Member

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    Thanks for your help with finding a Melbourne jeweller Ben. Whenever you have time. I am in no hurry.

    Oh no. Adverse reaction to anti-inflammatories doesn't make things easy. I hope you are working with a rheumatologist? It's better to address the problem sooner rather than later.

    Oh wow! In your teens? That is much earlier than I thought. I think it is fair to say that it is your life-long passion. I hope things have gotten easier for you. What doesn't kill you makes you stronger.
     

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