I am having trouble getting the last common treasure from the Dirn Khibhar Mines. I counted 43 common treasure chests in a row giving the mana leaf item. I've gotten the health berry there before, but not in this session. During this time, I got a gold chest, four silver chests, and two mimic chests. The third common loot is still unknown.
Rare treasures are obtained using a simple formula:
1. Treasure Finder in small Inventory.
2. Good clothes (for example, an elven set) and speed and magic skills.
3. Well, a series of victories, the creeps make the indicator of the probability of a rare treasure appearing red (displayed on the left side of the location status line).
If you leave the location, your series of victories is interrupted.
More details: in the Agranor library.
Ah, so it is a greater alchemite. I noticed similar behavior with the common treasure greater alchemite in the dark cave. It seems that the inherent rarity of the greater alchemite as common treasure is so high that it's considerably faster to farm them as rare treasure with the treasure finder.
edit: I just got five of them in a row. Weird.