This module deals with the materials used in making concrete hollow blocks. Topics discussed include: (1) igneous, metamorphic, and sedimentary rocks; (2) weathering (the process of breaking down rocks) and its effects on rocks; (3) cement; (4) stages in the manufacturing of Portland cement; and (5) the transformation of cement into concrete (outlining, in an appendix, chemical changes in the process). A mastery test (with answers), answers to questions asked in the module, a glossary, and list of references are included. (JN)