Rocks and other Earth materials are included in national, state, and local standards. For example, "A Framework for K-12 Science Education" (NRC 2012) contains topics related to Earth systems, which include the hydrosphere, atmosphere, biosphere, and geosphere. By second grade, students should be able to describe how most areas where plants and animals live contain rocks, soils, and sand (Dimension 3: Disciplinary Core Ideas-Earth and Space Science ESS 2.B, p.183). By the time they enter preschool, most children have some preconceptions about the properties and uses of rocks, some of which may be nonscientific. When asked to describe hand samples of rocks (i.e., a rock that can fit into the palm of the hand) children immediately respond with the properties of size, shape, and weight. While these aspects are observable properties of rocks, they are not helpful to geologists in identifying individual types of rocks. Typically, students also tend to confuse properties of minerals, such as hardness and luster, with properties of rocks. The lesson described in this article provides an example of how the authors help uncover what young children already know about rocks, address misconceptions, and help children begin to construct a scientific understanding of properties of rocks. Children also develop their scientific practices by observing, recording, and analyzing data about rocks, while deepening their understanding of Earth materials. Although the authors use this lesson in their preschool classrooms, they also offer ways to modify the lesson for older children.