A block of stone, peña,[1]​ pedrejón,[2]​ or gauge,[3]​ is a fragment of rock larger than boulders but that is loose, so that it can be moved by natural mechanical processes such as water currents, earth movements or the force of gravity on sufficiently steep slopes. When using the word "block" no distinction is made in shape or type of rock or mineral, although they are generally angular and faceted pieces.

Although, in general, the blocks can become very large, other times reference is made to "small blocks", manageable by humans, when talking about angular fragments of stone that, having recently been broken off from the bedrock, do not still maintain living edges "Arista (geology)"). For this type of material it is preferable to use the word clast.

Within the granulometric classification of soil particles, the blocks occupy the following place: