Silver mining is casino-floor slang for walking from one slot machine to the next in search of coins or credits that other players have left behind. The “miner” checks machines as soon as their players walk away, hoping someone forgot a coin or two after collecting a payout.
The habit is also called slot walking, a playful twist on sleepwalking: miners seem to drift aimlessly from machine to machine as if they were not quite awake. Knowing the term is mildly useful; knowing that the practice exists is more important. If you play slots in a land-based casino, keep an eye on your coins and never leave them unattended, or there may be fewer waiting for you when you return to your seat.
Silver mining on the floor and online
Land-based operators deter it with ticket-based cash-outs, floor staff and the eye in the sky. Online there is no tray to raid, because credits sit in a password-protected account balance; the nearest equivalent risks are shared devices and hijacked sessions, which session timeouts and login alerts help to contain.