A method was developed for fabricating transparent glass casts of fractured rock pairs. These glass casts provide reproduction of surface topography and roughness of natural fractures, optical clarity, and representative wettabilities of mineral surfaces. The glass casts are an improved tool for studying flow and transport in fractures compared to previous approaches. The surface of a clean glass fracture has a contact angle near zero, and more importantly, the surface wettability can be intentionally altered with chemical treatment. Glass casts of rock fracture surfaces may be used for visually and quantitatively studying various physical, chemical, and microbial processes occurring in rock fractures, especially when multiple fluid phases are involved. ¿ 2000 American Geophysical Union