Exploring communication dynamics in digital social spaces such as massively multiplayer online games and 2D/3D virtual worlds has been a long standing concern in HCI and CSCW. As online social spaces evolve towards more natural embodied interaction, it is important to explore how non-verbal communication can be supported in more nuanced ways in these spaces and introduce new social interaction consequences. In this paper we especially focus on understanding novel non-verbal communication in social virtual reality (VR). We report findings of two empirical studies. Study 1 collected observational data to explore the types of non-verbal interactions being used naturally in social VR. Study 2 was an interview study (N=30) that investigated people's perceptions of non-verbal communication in social VR as well as the resulting interaction outcomes. This study helps address the limitations in prior literature on non-verbal communication dynamics in online social spaces. Our findings on what makes non-verbal communication in social VR unique and socially desirable extend our current understandings of the role of non-verbal communication in social interaction. We also highlight potential design implications that aim at better supporting non-verbal communication in social VR.