Glory Alley and the Star Riders

Glory Alley and the Star Riders, by C. Deanna Verhoff, is a young adult sci-fi/fantasy about fourteen-year-old Glory Alley, amateur spelunker and geologist.  She lives on Tullah, a planet very much like Earth.  Glory's life isn't what you'd call "ideal" - it's anything but.  Her mother died after giving birth to her youngest brother, and things have been going rapidly downhill since then.  Her father is a drunk, and alternates between being Mean Dad or Nice Dad, but with their family's financial situation being what it now is, coupled with her father's abusive behavior when drunk, the authorities have been a presence looming over the family.  Despite his drunken meanness, and the fact that the Alley family is pretty much the town joke, Glory would do or give anything to keep them all together.  

Little does she know that one solo trip into the caverns at Queen's Mesa will put into motion a chain of events that will change her and her world forever.  

Everyone has heard the stories about the Elboni, but to the people of Tullah, the stories are just myth.  Glory isn't sure what to believe anymore when she barely escapes from the Mesa with her life after picking up a beautiful stone, unlike anything she's seen before either in books or with her own eyes.  Could all the stories be true?  Everyone except her grandfather thinks she's gone crazy.  When three strange-looking men come looking for something, though, she realizes that the stories may indeed be true, the stone she found is much more than what it seems, and there is much more to the universe than the science of her world has been capable of uncovering so far.