Question about SNES cartridge connectors

[ZidanaX]

Hello, I've been cleaning my SNES carts, and noticed something weird: even after I don't get any more grey on the q-tip, all of my connectors still have this grayish/blackish stuff on the half of the connector that's closest to you when looking at it straight on. (though I need to look under a bright light at an angle to see the grey) Yet the other half is generally a nice shiny golden color. Is this normal?

[omnedon]

Well, depends how clean you want your carts. If you disassemble the carts, and take a fiberglass brush and/pr white eraser to them, you can often make them all gold colour again.