Ultrasound Testing fullproof?

Discussion in 'Bullion Investing' started by bullibags, Nov 12, 2015.

  1. bullibags

    bullibags New Member

    Hey Guys so an ultrasound thickness tester can tell you if your gold bar is solid and not filled with something else for example tunsten. Now gold has a speed of sound of 3240 m/s. but what about 14k or 18k does anyone know is it very negligable? if so wouldn't that mean that part of the bar could be 24k and the center 18k and give you a similar read, hence you losing money?
     
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  3. desertgem

    desertgem MODERATOR Senior Errer Collecktor Moderator

  4. Brett_in_Sacto

    Brett_in_Sacto Well-Known Member

    There are some (very expensive) XRF devices that can immediately tell what is in the metals.

    Example: http://www.ebay.com/itm/SPECTRO-XSO...ometer-MICRO-3MM-SPOT-SIZE-GOLD-/311417445361

    I brought a bunch of mish-mash melted down silver to a guy that had one. He was able to sample big chunks (1-2 inches thick) and tell me the exact amount of silver in each. We also found that they were 62% silver, 1.8% platinum and 2.3% gold - so I scored when I sold him the scrap. (I gotta believe this was some sort of industrial or dental metal?)

    I paid $80 for almost 3 pounds of the stuff in a glass jar at a GSA auction. People thought I was nuts for buying melted slag and lead. It was labeled silver, and none of the pieces stuck to a magnet - so I gambled. I ended up selling the jar for $600 when all was said and done.

    The XRF gun was able to identify each piece and show the variance in the metal content. Some shows more, some showed less - so it was obviously a failed smelt at some point.

    VERY accurate. I want one, but it would cost me more than I'd ever be able to recover by using it.
     
  5. ToughCOINS

    ToughCOINS Dealer Member Moderator

    @ Bullibags . . . Be careful with your assumptions . . . yes, an ultrasonic tester will differentiate between gold and tungsten of the same geometry. That is because the tester is measuring the fundamental natural frequency of vibration of the tested piece of metal (a function of both mass and stiffness). The test is beneficial for non-destructive testing for tungsten because the densities of tungsten and gold are virtually identical, but their stiffnesses are not.

    This test method cannot necessarily be relied upon to identify other combinations of metals intended to mimic the density of gold however, as metals both heavier and lighter than gold could conceivably be sandwiched together to produce the desired result. With time and inclination, I'm pretty certain a very deceptive gold-plated sandwich metal could be developed. To detect that, a different test may become necessary.
     
  6. desertgem

    desertgem MODERATOR Senior Errer Collecktor Moderator

    XRF spectrometers are limited in the depth of sample they can accurately analyze. Depending on density, the depth many be in micrometers, up to 50+millimeters in soft minerals such as coal. That is why the wavelength device was used to analyze the 1000 oz gold bars such as in storage instead of XRF.
     
  7. Brett_in_Sacto

    Brett_in_Sacto Well-Known Member

    Very good to know. I was considering buying one "someday" as I move farther away from my real job and into hobby/semi-retirement. Learn learn learn!
     
  8. tortoise62

    tortoise62 New Member

    I stumbled across an ultrasound tester which seems to be affordable. The problems is with gold American Eagles - they aren't 24K gold. They are 91.67% Ag 3% Ag and 5.33% Cu. While this mixture was created for durability, it reduces anti-counterfeiting via ultrasound. The U.S. Mint is doing nothing to thwart Chinese counterfeiters. https://fisherpreciousmetals.com/us-mint-on-anti-counterfeiting/

    Canada has Bullion DNA -
    Although damage to the coin can prevent authentication, at least it's something. It's good for gold dated 2014 and newer; silver 2015 and newer.

    Sounds like China will make a ton of cash pumping out gold plated tungsten fakes. Watch how this silver bar tricked XRF testing:
     
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