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Colour Change Sapphire

This topic contains 11 replies, has 5 voices, and was last updated by Profile photo of huttonit huttonit 10 months, 3 weeks ago.

Viewing 12 posts - 1 through 12 (of 12 total)
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  • #200207
    Profile photo of sydp
    sydp
    Participant

    Hi, thought I would start a conversation on gemstone hue and the opinions of what constitutes a colour shift/colour change in gemstone
    I have attached a colour change sapphire from Africa that I cut myself from the rough.
    I call it a colour change but some other gemmologist may not.

    #200227
    Profile photo of raghu
    raghu
    Participant

    Beautiful sapphire sir.
    Could you please tell me how to photograph gems

    #200246
    Profile photo of sydp
    sydp
    Participant

    The best way to photo gemstones are to use a camera with macro lens.
    you can use a Iphone but not as good.

    #200247
    Profile photo of rpentney
    rpentney
    Participant

    Since the color seems to change according to the direction the light is coming from, why would it not be color change? Is the composition of the light different from one photo to the next? (day light / incandescent etc.)

    #200249
    Profile photo of raghu
    raghu
    Participant

    Thank you for your advise on photography

    #200250
    Profile photo of steve
    steve
    Participant

    Hello everyone. I am a new member who lived and worked on the Anakie Sapphire Fields in Central Queensland, Australia for 19 years. During that time I found a few sapphires that exhibited a strong colour change from green in daylight to pink under incandescent light. The effect was more pronounced in facetted gems. Some of these stones displayed a pinkish tinge even in daylight and were highly sought after. I have looked at the photos of the sapphire you cut and it is a very beautiful stone. It shows what I would call a change in the tone of the colour rather than a change of colour but having said that you have a very beautiful stone no matter what name is given to it and that I think is the most important thing of all.

    #200364
    Profile photo of sydp
    sydp
    Participant

    Thank you all for your comments,
    When I was undertaking the GEM A Diploma and preparing my student project on colour change gemstones, I believe I read this from an article of the Gemmological Institute of America that if there is a 20% shift in colour/hue then it is deemed to be a colour change gemstone.

    once again thanks for the comments

    #200476
    Profile photo of huttonit
    huttonit
    Participant

    Based on your photos I would definitely describe it as colour change.

    I have attached photos of a colour change sapphire my wife has as a comparison example. The differing colour is totally dependent on the change from natural light and white light. The stone is very well cut and has no zoning.

    Attachments:
    1. 2015-07-27-11.50.03

      2015-07-27-11.50.03.jpg

    2. 2015-07-27-11.50.12

      2015-07-27-11.50.12.jpg

    #200508
    Profile photo of sydp
    sydp
    Participant

    Nice gemstone do you know origin.. The sapphire I put online is either Tunduru or Songea East Africa

    #200626
    Profile photo of huttonit
    huttonit
    Participant

    I can not tell you the origin of the stone. It was part of an inheritance from my mother-in-law, in the box is the original receipt dated 1937 for £21 Gineas (£22 4s 6d) suggesting it was my father-in-law’s mother who originally had it: they lived in London and owned a meat suppliers to restaurants in central London. The setting is Russian, which originally set the alarm bells ringing but having tested it and examined it under a microscope I am 95% satisfied it is not lab due to the sharp natural inclusions seen at X60 at X10 it is almost clear. I do suspect the setting is not original because of solder marks left on the clasps, suggesting it had a different stone in it and this one replaced it or it was re-mounted for some reason. Now when that was done there is no saying but the stone is exceptional and the change is so obvious I was surprised that it wasn’t Lab.
    It is 6.97ct (calculated), RI 1.68, SG unable to check without unmount, and 11.5 mm round. I estimate the blue/Purple to be 148-151 and the pink to be 181.
    It could be worth anything from £10,000 for the stone alone, but have no intention of selling it.
    I hope you enjoy it because my wife and I certainly do.

    #200628
    Profile photo of sydp
    sydp
    Participant

    Hi Huttonit, thanks for the info, but I am a little confused in relation to your RI reading 1.68.
    if this is corundum it should be between 1.762 – 1.778 with a Birefringence of about .008 Negative. If you do not get these readings or close to them then I would suggest it is not sapphire.
    Although if the table is cut at 90% to the C Axis of the crystal I can understand that you could get a single refractive reading from the table but once again it would fall in the range of the above for corundum.
    hope this helps.

    #200630
    Profile photo of huttonit
    huttonit
    Participant

    You are right. Typing without my glasses on. It is 1.768.

    Well spotted.

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