"It's beautifully cut and polished to a mirror-like surface."
Blue Gemstone is a key item that can be found in Resident Evil.
It can be used in the room with the tiger statue to procure a box of shotgun shells.
The blue gemstone can be found in the dining hall of the Spencer Mansion after pushing the statue over the edge on the room's second floor balcony.
In the Remake, even if you didn't push the statue over the edge, it will lie broken on the ground of the dining hall when you come back from the dormitory.