Volatile cycles between Earth’s atmosphere, lithosphere, cryosphere and hydrosphere play a critical role in planet evolution. Carbon, oxygen and hydrogen are the dominant volatile elements, and Earth’s mantle is the largest reservoir of these elements. One of the most important volatiles on Earth is water. Water exerts key controls over the properties of magma, mantle convection, the composition of the Earth’s atmosphere, and the evolution of life. This project will investigate water in the mantle transition zone (410–660 km depth) and deeper. A small proportion of diamonds, carried to the surface by rare and rapid volcanic processes, encapsulate minerals during their growth. These minerals are among the deepest direct samples available of the Earth's mantle. The project will use a collection of diamonds hosting such minerals to determine the water concentrations of the mantle where the diamonds formed. The project will also expand a large interactive exhibit in the Minerals Hall of the American Museum of Natural History into a web-based version on a platform for children and youth, called OLogy, and hosted by the museum. The new web version will be tested in upper elementary and middle school classrooms. Water is one of the most important volatiles on Earth. This project will investigate water in the deep regions of the planet, such as the mantle transition zone (410–660 km) and the lower mantle (660–2900 km), by studying mineral inclusions in diamonds. A small proport