Formed in rocks over millions of years, most caves are composed of limestone, dolomite, gypsum, and marble. Some limestone caves are decorated with cave formations called speleothems. Two commonly known speleothems are stalactites, which hang on the ceiling, and stalagmites, which grow up from the floor. In the book, In Search of Hidden Treasure, the children in Mrs. Wigglebum’s class learn about the natural treasures found in a cave habitat. POs: Download Order Form