The Blue Gem's purpose was to open the gate to Raccoon City Hall. On the last fortnight of the Raccoon City Destruction Incident, it was stolen along with several other Gems. It was found in the body of a Restaurant owner.
The Gem was kept in the evidence locker until eventually retrieved by Jill Valentine on the 28th of September. Before checking, the name of the item is Blue Gem. After exploring, the name is Sapphire.
Initially, the clock, that contains twelve different gems lacks two of them. One of them is sapphire. "A clock is not functioning. Two gems are missing from the hour plate." says the clock, when it's explored for the first time. "It seems that this is not enough to make the device to work" says message after setting one of the gems. The gem disappears from the inventory after setting and can be seen on the clock.