Okay- 1990s cartoon with power-ups from gemstones or jewel-like things. I'll throw out a few possibilities that come to mind.
Captain Planet and the Planeteers- The Planeteers used their individual rings to call on their powers and also combined their powers to summon and create Captain Planet.
An '80s cartoon called "Visionaries: Knights of the Magical Light" also bears some similiarities-
Another '80s cartoon called "The Adventures of the Galaxy Rangers" also featured a form of powerups.
And here's one other '90s show that may be it-
Tenko and the Guardians of Magic
http://en. wikipedia. org/wiki/Tenko_and_the_Guardians_of_the_Magic
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