I have a real weakness for crystals and things with 'cores' so naturally seeing Magicite as seen in Final Fantasy 6, I was inspired to create it in 3D (as well as get practice rendering crystals)
Just because I couldn't help myself, I also threw in variations on the classic green mineral.
Green Esper Magicite (Magic)
Blue Spirit Magicite (Techniques)
Gold Royal Magicite (Summons)
Black Space Magicite (Time and Space)
Supposedly when a human holds these, they gain power from it. Sounds a little like materia (which followed close after in FF7.)