There are several Red Jewels seen.
Red Jewel in RE 2
Raccoon City Police Department
There are two red jewels in the RPD. One can be found if the fireplace is lit. This melts part of the painting above, which exposes the jewel. The second is found after solving a short puzzle by pushing statues. They are needed to get the King Plug in Leon's scenario, or one of the halves of the Jaguar Stone in Claire's scenario.
Apple Inn
Found in the safe in Room 306, it is used to open the door to the Lobby.
Raccoon University
Found in the Raccoon University, it is hidden in the clock in the General Manager's Room and is released when the clock strikes "3:25" on "Easy", "10:05" on "Normal", "7:40" on "Hard", "2:50" on "Very Hard."