Resident Evil 5 - Secret Heart of Africa gem
Chapter 5-3: Between the stairs during the Jill solo fight after you ended the previous fight by damaging Wesker enough to make him retreat.
To get the Heart Of Africa treasure, you must do a set number of damage to Wesker during the first fight with him and Jill. The best way is to have the Infinite Magnum. You will also get the "Bad Blood" achievement. After you defeat him and start the Jill fight, the treasure will be between the two curved staircases. Also, do not forget to get the gem in the southeast corner of the room you enter in the crate, the two in the tombstone upstairs, and the one nearby in the little pot.