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Paraiba or Copper Bearing Tourmaline, How can I know?

This topic contains 1 reply, has 3 voices, and was last updated by Profile photo of gemguy gemguy 2 years, 2 months ago.

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  • #177907
    Profile photo of terry
    terry
    Participant

    I have several beautiful Tourmaline that I think are Paraiba Tourmaline. However, before I invest the money to have them certified so I can sell them, I need to know if they are copper bearing & thereby worth the expense. Is there any test I can perform to see if they are copper bearing?

    #177908
    Profile photo of gemguy
    gemguy
    Participant

    Hey Terry –

    Most any competent gemologist can ID it as Tourmaline. However, you need spectrographic instrumentation (a spectrometer) in order to establish the presence of copper in Tourmaline.

    If you check out our “Appraisals” tab we provide a gem identification service that (for our members) is only $55 and our lab can identify cuprian (copper presence) in tourmaline or lack thereof. You could then send it to GIA for their certificate knowing it is indeed copper-bearing tourmaline.

    #177921
    Profile photo of terry
    terry
    Participant

    I thought about id’ing it with a spectrometer, my GIA text book says that that test is inconclusive as it varies so much. I was wondering about an electrical test, such as a diamond tester. Copper is electrically conductive, that’s what a diamond tester uses to test diamonds and moissanite. Anybody ever heard of something like that?
    Also wouldn’t I use the IGS system for a positive ID? They have cert’s available with photos for $120.00 to members. Or do you think a GIA certificate is better?

    #177963
    Profile photo of gemguy
    gemguy
    Participant

    You would need to send it a lab with proper experience. IGS uses a lab partner that is equivalently equipped to the GIA laboratory (full suite of equipment, including raman spectroscopy). The equipment required to accurately detect copper at Paraiba-level concentrations is extremely expensive, and requires operator expertise. If the question is whether a GIA Certificate or an IGS Certificate is more universally recognized, GIA is clearly more recognized. It is also much more expensive for larger-sized stones, and they charge you additional money for an opinion of origin. The IGS certificate is far less expensive, and uses a comparably equipped lab. Most people who intend to certify their stones to sell them send them to IGS for an ID report (no picture) to know what they have before they go buy the very expensive cert not knowing how it will turn out. If you spend the money to get the cert, and it doesn’t come back copper-bearing, you are out a lot more than the $55 you pay to get a positive ID. For folks who just want to know exactly what they have in their collections, those folks typically get a printed cert.

    Using magnets to identify Cuprian Tourmaline? Unfortunately no, magnets won’t work. The amount of copper impurities in allochromatic tourmaline is generally very low. Concentrations as low as .05% by weight are relatively standard fare, and the highest concentration remains about 2.5%. At these levels, it is highly unlikely that copper in Paraiba Tourmalines would be detected with any magnet, except perhaps at the very highest concentration, and even then, not reliably so.

    Also — Copper ions (Cu2+) have only one unpaired electron, and are not that magnetic to begin with. There is sometimes a strong magnetic attraction found in allochromatic Paraiba Tourmalines but it is likely due to the manganese content, not the copper. In Paraibas, manganese is often present in much higher concentrations than copper (up to 6.1% manganese oxide by weight). Iron is also found only as a trace element in Paraiba Tourmalines, but again, it is found at such an extremely low level of iron is not magnetically detectable.

    Regardless…. even if it was magnetic, there are too many confounding trace elements for a novice with a basic spectrometer to reliably assign a “Paraiba” designation based solely upon magnetic reactivity or lack thereof.

    #178075
    Profile photo of ae6st
    ae6st
    Participant

    Would an ohm meter work or is the insulation to conductivity too high in the stone to get a resistance reading?

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