Cleaning contacts with an eraser is a very bad practice. The gold flash is only about 20 microns thick and can easily be sanded off with the eraser. If you get down to the copper, the connection to the sock will be VERY unreliable, and you've successfully ruined your memory module!
The only eraser I've ever used on them is a non-abrasive Mylar drafting eraser, which doesn't remove the gold flash.
The only eraser I've ever used on them is a non-abrasive Mylar drafting eraser, which doesn't remove the gold flash.