Minerals at school

Children define “minerals” and “rocks” on the basis of their previous experiences and ideas. In their opinion, minerals are found only in mines and in the subsoil, and rocks only in the mountains. Minerals are always glittering or transparent and rocks are grey or brown and have a opaque appearance. So they often attribute a high economic value to minerals whereas they consider rocks as a natural material without relevance. These ideas are deeply rooted concepts (Stokes et al., 2007) that undermine the building of scientific knowledge about minerals and rocks. It is necessary to be aware of these naive thoughts, to dismount them in order to build a scientific reasoning (Libarkin et al., 2003). The pedagogic literature, as well as our own experience, indicates that the direct experience is a necessary step (even not sufficient) to face with this difficult and delicate passage, through a constructivist approach so that “what the pupil learns he at least understands” (Dewey, 1930). We describe a didactic research, carried out during a PhD program of Department of Earth Science of University of Pisa, in which we tested an experimental learning sequence about minerals in seven classes of the middle school, involving approximately two hundred pupils. At first, the teacher divides the class in small work groups, formed by three or four pupils, and gives them three well crystallised minerals. The pupils have to describe what they see. Pupils discuss within each group and - at the end - the teacher asks them to share their ideas. Naive concepts about “minerals” and “rocks” emerge clearly during the discussion; when invited to describe more details, pupils use words such as shape, faces, edges, corners, points etc. and the teacher highlights these words and their relationships with solid geometry. The teacher slowly leads pupils to a shared definition of mineral and then drives them to suggest the possible differences between minerals and rocks. The teacher exhorts pupils to describe the crystal habit of the three minerals by using more scientific words, found in internet through a guided search. At this point the teacher gives nine or ten different minerals to each group, with a form to be filled with some properties of minerals: shape, lustre, transparency, hardness (scratching by fingernail, nail, none of them), streak, cleavage or fractures, specific gravity, magnetism, HCl reaction. Every group tests these properties on each sample and fills in the form. Pupils use the collected information and a dichotomous key to discover the name of their samples. The starting question-key of this inquiry approach is “What are minerals and rocks for you?”. Pupils have the time to freely observe different samples and they investigate some properties of minerals with simple experiments. This work allows them to reflect individually and in group, developing and sharing new ideas and modifying the old ones, at the light of their new knowledge. Dewey, J. (1930): Democracy and education. An introduction to the philosophy of education. McMillan, New York. 436 p. Libarkin, J.C., Beilfuss, M., Kurdziel, J.P. (2003): Research methodologies in science education: Mental models and cognition in education. J. Geosci. Educ., 51, 121-126. Stokes, A., King, H., Libarkin, J.C. (2007): Research in science education: Threshold concepts. J. Geosci. Educ., 55, 434-438