Charmed Forces — Melissa J. Morgan

"Maybe the amethyst really does have special powers," Alyssa said.
"Of course it does," Sloan said. "They all do. Why else do you think your prediction came true?"
"Come on, girls," Mandy said. "Let's not blow this all out of proportion. It's a coincidence."

But is it a coincidence? The members of bunk 6B have been sworn to secrecy: Alyssa is in possession of a seemingly magical amethyst, and some pretty weird things have been happening. Ever since she found the purple stone on the campgrounds, she's been accurately predicting her bunkmates' futures and interpreting their dreams. But some of the girls are skeptical, especially when Alyssa predicts that it's going to snow at camp this summer. Now that's just ridiculous! Isn't it?