In this FACTivity, you will grow your own speleothem. At the end of this FACTivity, you answer the following question: What does this activity tell us about the formation of speleothems? Materials (for each student or group of students): Pictures of decorated cave passages Epsom salts, washing soda, or baking soda (Epsom salts and washing soda are more likely to form larger formations) Warm water 2 plastic cups of the same size (preferably clear or see-through) 1 piece of aluminum foil to make a Topics: Carbon, Water, Cave Formations, Hands-on, Modeling, Simulation, Speleothem.