Can be improved using a Master Jeweler's Scroll.
Complete the quest from the Master Jeweler's Quest Scroll and get the Master Jeweler's Scroll, which can be used to upgrade Gem.
The gem is not stable and with each level its life time is reduced by 1 hour. If you do not improve the gem or exchange it for rewards before the expiration date, then you will be left with nothing!
Gems of any rank can be exchanged for rewards at the Gem Exchanger on Mirage Isle.
