Rock surface hardness is often used as an indicator of the degree to which a rock surface has weathered. As the surface deteriorates the loss of cohesion results in crumbling of the surface, increased pore water circulation and dislodging of sections such as flakes. It is widely assumed that this results in a lowering of rock surface hardness. However, hardness can also increase if weathering leads to cementation of the surface due to the deposition of solutes such as quartz, clays and small quantities of carbonates. A number of different instruments are available to map out hardness distributions and changes over time. This chapter outlines the use of a simple field test (Moh’s hardness test), three rebound devices (Picolo, Equotip and Schmidt Hammer) and resistance drilling as possible methods for assessing rock surface hardness.