The rules say that opium can be used in place of any resource, and that "each time the player uses 1 opium" they mark it on their player board. There seem to be several ways to spend opium:Yes, all of the above are marked on a player's board. There are the exceptions: If you do "2 for 1" or use MARKET to do "1 for 1". You can use the opium without marking on a player's board.
* opium in place of 1 resource
* opium spent to buy the Opium Den building
* opium exchanged using the Opium Den
Are all of the above marked on a player's board?