Thunderbird. Prentiss Twins, #1

Janine Prentiss is tired of spending her summers digging up dinosaur bones with her single-parent father, an eminent paleontologist. But neither does she want to spend her summer vacation listening to her shaman grandfather's lame tales of spirit quests and totem creatures who talk. Justin Prentiss thinks his twin sister is nuts. What kid in their right mind wouldn't love field camp? The wild beauty of Montana mountains, fresh air, and adults too busy to pay attention to what a guy is doing as long as he shows up for meals and bedtime.
Field camp rocks!At least until Janine finds a weird chunk of granite that she's convinced is a living egg...