Crystal Heart - The Life Crystal Chronicles, #1

When Mellissa Hail meets the magical changeling Gregory, she discovers a hidden world of magic and wonder. Now she must come to terms with believing in magic and a destiny inherited from her ancestors. Together Mellissa and Gregory set out on a journey to keep the peace between worlds. But time is running out. The seal that guards the evil leprechaun Kadon is breaking and darkness is sealing into the earth.
Can Mellissa save mankind in time?