Mellbreak is formed primarily from the laminated mudstone and siltstone of the Kirkstile Formation. There is an intrusion of basalt on the Crummock face and the southern end around Scale Knott exhibit the Buttermere Formation. This is an olistostrome of disrupted, sheared and folded mudstone, siltstone and sandstone. The rocks of Hen Comb are of the Kirkstile Formation, laminated mudstone and siltstone, often associated with the Skiddaw group.