The rock cycle is a key component of geoscience education at all levels. In this paper, we report on a new guided inquiry curricular module, "Sleuthing through the Rock Cycle," which has a blended online/offline constructivist design with comprehensive teaching notes and has been successful in pilot use in Rhode Island middle and high school classrooms over the past 3 y. The module consists of two overarching activities: (1) SherRock Holmes and the Case of the Mystery Rock Samples, and (2) Cracking the Case of the Changing Rocks. The module encourages hands-on activities, peer collaboration, and real-time teacher review of embedded textual and reflection components. Overall, Rhode Island teachers report that the module is an outstanding teaching tool and that the associated professional development is empowering.