You are a US citizen and: 1  You are a first time applicant age 18 or older. 2  OR your most recent U.S. Passport was issued when you were under age 16. 3  OR your previous U.S. passport was issued more than 15 years ago.
Cave formations are called speleothem, from the Greek word spelaion, cave and thema meaning deposit. Almost all of them are made of calcite, the crystal of calcium carbonate. Different minerals and different movements in the water account for an incredible variety of cave formations.
Giant Crystal Cave. 1  Giant Crystal Cave is situated above a magma chamber, that emanates great heat, and due to the mineral rich water originally in the cave, the undisturbed environment and hydrothermal circulation, the huge crystals had the opportunity to form over thousands of years.