Minerals are commonly taught in ways that emphasize mineral identification for its own sake or maybe to help identify rocks. But how do minerals fit in with other science content taught? The author uses mineral formulas to help Earth science students wonder about the connection between elements, compounds, mixtures, minerals, and mineral formulas. This weeklong 5E learning cycle (Bybee 2014) lesson has been used with middle school students being introduced to the periodic table as well as high school students in Earth science, physical geology, and chemistry. The unit addresses the Next Generation Science Standards (NGSS Lead States 2013; see p. 23). This lesson focuses on the mineral-classification-by-formula portion of the unit.