Blue streaks on a silver bar

Just got another 2 PAMP kilo bars today and noticed that these two had really unsightly blue streaks all across them. Anyone know what these streaks are, what causes them and if they can be safely removed? Thanks.

 

Thats a signature feature of all pamp bars.

Its peculiar to the crystallization size of the metal and depends on cooling speed.

A great anti-counterfeit feature imo. Every pamp kilo bar i have has it. Its visible because of diffraction patterns in certain direct lighting.

 

Strange. The first bars I got were streak-free. Does this develop only after some time?

 

I have "2d hologram" rainbow-ish colour markings on most of my pamp bars, but they're in a radial pattern not just horizontal streaks. I'm guessing that's caused by what intelligencer said

 

all of my bars have it....i'd say its pretty standard for the swiss pamp bars......

 

Thanks all for the responses. I'll keep an eye on the others to see if they do eventually develop the streaks. I was ready to stack only PAMP bars but now... generic in-house 5kg bars may not be so bad after all.

 

I actually like them they add character - + they don't change the sell $