[Clean]

Take out one of your usb connectors, and look at the metal piece. Notice that the mark on the metal from it being put in and out the slot so many times. What is that mark? I mean how was it produced, has the metal been pressed in, or have small metal particles been sawed off, or what?

Thank You

[billnotgatez]

My guess

scraping or wearing down by friction
    abrading
    chafing
    erosion
    grating
    rubbing
    scratching
    scuffing

[Clean]

so every time we pull out our usbs metal dust enters the atmosphere... :|

Sorry for making this explicit, it is a bad habit of mine.

[Arkcon]

Not really.  They may rub of against each other, or the microscopic flakes of metal, even if we can't see them, may simply fall to the ground.

[Enthalpy]

The metal can just deform but stay at the part. This is expected from gold. It's also the normal behaviour of most materials at the final steps of polishing, where no material is lost.

[Clean]

I did not know that metal can deform like that Enthalpy, interesting.