Fairy powers manifested around the time they turned thirty but what they looked like when they were born always matched what they would be. For example, Flora's hair was green and made of vines and she had skin the color of tree bark.
Ruby's case was so bizarre that her parents had no idea what her powers would end up being until they appeared on her thirtieth birthday. She had been out digging holes in the backyard, loving the dirt as all earth fairies do, when the earth began to shake.
Her parents felt it and came out to see what was wrong immediately only to find their daughter buried under a mountain of jewels. It took a while to dig her out and realize what happened.
Simply by sitting on the ground, Ruby had summoned every jewel beneath the earth for miles. Buried treasure…jewels in mines…natural mineral deposits. She had control over any stone that came from the earth.