I was mentioned by W. Eric Martin in his Blog. He linked to the 2 and 3 player variant of Mines of Zavandor. The original post was in German, so here the English translation:
Use the 4 player rules and set up.
2 players: Use 2 blocking markers to block 2 rows. In the first round the emerald (#2) and ruby (#4) rows are blocked, i.e. you can't buy theses cards in this round. At the end of the auction phase, remove as usual all left over cards (including the blocked cards) and move the upgrade markers to the other two rows (#1, #3). Now the cards in the sapphire and diamond rows are blocked. In the next round the block tokens move again to row #2 and #4 and so on. This is not much to handle and now only 2 cards per round are available!
3 players: Use one blocking marker starting in the ruby row (#4), moving down one row each round (4->3->2->1->4->3...). A blocked card may not be bought and is removed after the auction phase.