Previous studies have shown that mathematicians employ lengthy silences in their collaborations, contrary to the norms that govern every-day collaborations (e.g. Sacks, Schegloff, & Jefferson, 1974). Such results shows the relevance of an investigation of silence in mathematical collaboration. This dissertation builds off these results in a series of three papers. The first paper describes a methodology that can be employed in the investigation of silence in mathematical collaboration. The second paper analyses silence in the mathematical collaboration of students in junior-level introductory proof classes. It identifies two forms of mathematical activity, reading and ruminating, that students regularly engage in, and which violate the norms of every-day conversation. Furthermore, it shows that these activities interact with each other in complicated ways. The final paper explores the norms that govern silence in mathematical collaboration. It finds that in their conversations, mathematicians display ongoing thought to conversationally relevant mathematics, and that this display of continued engagement with conversationally relevant mathematics allows lengthy thinking silences to come in the middle of conversation.