Recently an issue has proved to be quite popular around the forum. Is the combination "pyroblast + mana ruby" broken? And in the advent of our upcoming sourcebook, I decided to analyze the use of mana gems if you decide to implement our new Mana Point System. 
I won't give away the intricacies of our newest optinal rule; however, I will indulge to this complex matter. Many takes for a resolution were given in the refered thread (http://forums.white-wolf.com/viewtopic.php?t=69090) and I'll try to get the best out of it. Let's consider it part of the unofficial errata.
- Channeling spells can't be kept inside a gem after channel begins.
- A new mana gem will destroy the previous one, regardless of type.
- Mana gems can be detected by a careful caster using any spell detection.
- Treat mana gems like any other magic item in possession of the bearer and which can be destroyed if hit in combat. (totally optional, since some GMs are afraid of casters.)
Let's consider a few things before we move forward.
- The main difference between conjure mana water and conjure mana gem is that one restores spell slots and the other readies a spell. (tabletop RPG)
- The main difference between both spells is that one recovers mana while out of combat and the other while in combat. (WoW MMORPG)
If you change the way it works in a mana point system, it will make both spells work the same way with different names... A little lame and kind of pointless. Either way, I will provide the proper usage of Mana Gems if you were to change it to our current mana system*.
Mana Jades restore 5 mana points.
Mana Citrines restore 10 mana points.
Mana Rubies restore 15 mana points.
* The Mana Point system will be revealed in the upcoming e-book: Even More Magic & Mayhem.
