This experimental study explores how 60 primary-age children's (9-11 years old) understanding of rocks was effected by instruction that used the conceptual structure of the rock cycle together with the analogy of aluminium can recycling. Using a combination of probes into children's understanding, including concept maps and semi-structured interviews, changes to the content of their knowledge (description and classification of rocks) as categorized by membership of particular hierarchical explanatory frameworks (constructed from children's pre-intervention responses), and how such knowledge appears be organized into possible networks of information, are described. Results are then discussed in terms of the impact of the rock cycle, with or without the use of the analogy, on children's existing conceptions, followed by observations on the positive role of the analogy in supporting understanding. In conclusion, the implications for the nature of cognitive change in this domain as revealed by children's explanatory frameworks and the potential value of the aluminium can analogy in supporting children's understanding are addressed.