Wall games are a very geological form of light entertainment and education. I certainly have amused myself by identifying rocks and their features in walls since my days as an undergraduate and before. I was introduced to the name for the wall game (obvious, I know) by Eric Robinson (1996, 1997). Eric’s examples inspired me to devise my own version of a wall game in far-flung Jamaica. At the time, I was a member of the teaching staff in geology at the University of the West Indies in Mona, Kingston. Each semester, we took the first year classes for three one-day field excursions. As cash was getting ever tighter. I hit upon the money-saving idea of running one of the first trips on campus where there were various ‘urban geological’ features worthy of note. One of these was the stone base of a ruined building that had survived from Mona’s days as a sugar plantation. The rocks in the base were a marvellous mixture of blocks and rounded boulders, presumably collected from the bed of the nearby Hope River, which drains the mountainous country to the east of the university. This trip worked well and, after a few years, the late Trevor Jackson and I published a field guide based on my excursion (Donovan and Jackson, 2000).
The primary criterion for a geologically interesting and educational wall game is a good variety of rocks. The Mona wall game was most satisfactory in this respect, with a mixture of sedimentary and igneous clasts and worked blocks, and even one specimens with a fault running through it (Donovan and Jackson, 2000, fig. 3D-H). But such diverse compendiums of rock types are rare because stone walls have commonly been built from a local source of rock, such as from loose boulders in a river or collected when clearing a field (Anon, 2002). These are commonly composed of one type, that is, the rock that occurs in local outcrop (Nield, 2014). Yet I do not regard this as a problem – rather than searching for different rock types, you can still look for a variety of features shown by one or a few types of local rocks. For example, when on holiday in the White Peak of the Peak District of Derbyshire, I always examine the Carboniferous limestones of the dry stone walls for fossils.