Long-format answer: Explain why the concept of structure, rather than chemical formula, is more useful in the study of silicate minerals. Use olivine, pyroxene, amphibole and mica as examples in your discussion.
Question sheet 1 [no need to hand in]: I thoroughly recommend working through the question sheets provided with this part of the course. The first one has you downloading the crystal maker software and using it to examine the structural elements of crystals. This is an extremely valuable learning tool so do get familiar with it now.