When proximity mine tokens are placed, they must be placed beyond distance 1 of any other proximity mine tokens.
When a ship ends its movement at distance 1 of a proximity mine token, remove that token from the play area and roll two blue dice. That ship is dealt one facedown damage card for each and icon rolled.When a ship performs an attack, it can declare one proximity mine token as a target instead of attacking a ship or squadrons. The defending mine token is treated as a squadron with 1 hull point that is not friendly to any ship or squadron and has no keywords or defense tokens. If that token suffers at least 1 point of damage, remove that token from the play area.
Source: Rebellion in the Rim Campaign Guide