Oh, well hope the thread was helpful, check out some of my others
I'm back!!
I use Bernoulli/Archimedes' method quite accurately. I measure the delta weight of the plastic container with the bar fully levitating and submerged. Density of RCM bars using the same method is always within +/- 1%. This bar being off by 5% was a red flag of either air bubbles or imperfection from tungsten inserts. The ultrasound not passing was too much of a red flag.
Most of the methods you suggested Indigo are insufficient because they're mostly surface tests.
I'm going to do a youtube video on it, but to be absolutely 100% certain you have genuine bullion, there are 3 tests you need to do:
1 - density ( + weight of course)
2 - thru-bulk electrical conductivity measurement (Sigma Metalytics Pro, not the older one)
3 - ultrasound
4 - extra: diamagnetism test. Place strong neodymium magnet on a string, stand bullion vertically, and see if there is any attraction at all. There should actually be repulsion but the repulsion may not be detectable without fine instrument.
1,2,3 together are so robust that you don't really need anything else. It's a bit of an art learning how to do (3) properly.
XRF only does surface and should be avoided for confirmation purposes. No bullion dealers should be bothering to use XRF anymore for anything more than a first test before doing all of the above.
Unfortunately the vast majority of bullion dealers don't have the physics down as I do.
In the case of this bar, I got hold of the Sigma Metalytics Pro and it was very borderline unacceptable. The bar was just too sketchy. Not conclusive of tungsten. But all the measurements were slightly outside the tolerances. And ultrasound was way off. The dealer was willing to exchange it. If I were the dealer, I would have been scared when I saw all this!
Lesson learned is: only buy newer bullion bars. If any tests are not immediately passing, exchange it asap. Don't trust dealers to know what they're doing. You must learn the physics and verify yourself.
