The Learning in Science Project (Primary)--LISP(P)--investigated the questions and explanations primary children have about rocks. Data were collected during teaching sessions from New Zealand students (ages 8-11) and Australian students (ages 10-11). The teaching sessions required the teacher to create a situation in which children generated some questions about rocks. Students were then invited, either individually or in small groups, to offer possible answers to these questions. Additional data were collected during individual interviews. The majority of questions raised by students focused on the formation, composition, location, color, and durability of rocks. Specific questions generated and some of the explanations offered for each of these question areas are presented and analyzed. Additional analyses related to children's thinking revealed that their explanations can be categorized into looking for likenesses, linking different observations together, or using general ideas; the use of abstractions, however, was not noted. Possible sources of students' ideas about rocks (including their experiences with rocks, particle aggregation, and volcanoes) and implications for classroom practice are also considered. Stressing the importance of students' special language (and confusion surrounding the term "rock"), it is suggested that teachers use the term "rock" to refer to a material rather than an object. (JN)