Back in the old days when SEGA was in charge, these two minerals were used to manipulate the Clockworks in ways to bring certain enemies to the fray. However, since the pet update, these two minerals have been left to the wayside and I've been thinking on a way to use them since they're useless as they are at the moment.
One of the things that comes to mind is Sprite Gear: Because as it is currently, it is a MASSIVE Investment to be able to access anything beyond the basic collar. That's why I think having Moonstone and Valestone be used for making these Collars would be very helpful - provide new blueprints to make them, and give a new sense of progression outside of just a CR Farm that's focused on Vana.
That said, I wouldn't rule out the potential for 2 other pets if you really want to stick with how each mineral has its own pet assigned(red, yellow, purple).
Valestone could be used for a new pet that could reduce enemy resistances and be able to inflict Shock with its attacks, similar to how Drakon can inflict Fire.
Moonstone could be used for a different pet revolving around increasing allies Attack Speed and Damage, acting more as an offensive version of Seraphynx.
It's a thought, but I'm really wanting these two Minerals to at least see use and wonder what others have to say about it.
While certainly not the first time something like this has been suggested it does seem a bit odd that nothing has really been added to address the issue at all...
Perhaps beyond wanting new sprites there could maybe be some thought put into how to implement it...
At the moment the 3 Sprite tutorial/showcase missions are paired with the Alchemy tutorial missions in the 2-2 mission page...
Maybe.... the pair of new sprites should be something you can get later in the game.... The 10-1 rank mission page has 2 extra slots available on it's page... AND "The Collector" monster also makes a second appearance in the 10-1 mission "Breaking in the Recruits"
Wouldn't it just be perfect to have a new sprite given to the player at this time? One as a reward for defeating Vanaduke and reaching the core, but also it would help explain why the Collector has returned...