bigbaumer

My daughter is working on her 4th grade science homework, and her teacher is claiming that shells are abiotic, as well as dirt. I understand her reasoning for saying so, but I'm wondering at what point organic material like shells (once part of a living creature) and dirt (decomposing plant matter) goes from biotic to abiotic. The way I'm thinking about it is that I am thinking most rocks, especially sedimentary and metamorphic, would technically be biotic because they're made from biotic material...