Natural diamond in the Earths mantle is a metasomatic phase, crystallized from introduced fluids. Recent studies of diamond genesis have established the role of a variety of fluids (hydrous, silicic, carbonatitic and saline) in diamond crystallization, but many questions remain unanswered, including the relationships among different fluid types, and their ultimate origins. The nature of these fluids can be determined by studying micro- and nano-inclusions (minerals, glasses and fluids) in diamond, and the diamonds themselves, using a wide range of analytical techniques. Experimental petrologists recently have succeeded in synthesizing diamond from fluids which are similar to those found in natural crystals. One of the major aims of this session will be to compare the fluid species and the physical conditions of natural and synthetic diamond crystallization, and to map out directions for further research. Presentations on any aspects of natural and synthetic diamond properties that might contribute to our understanding of diamond genesis are invited. In particular, trace-element abundances in diamonds and their silicate and fluid inclusions and experimental constraints on diamond crystallisation conditions, their implications for natural processes, and industrial applications of this knowledge will be included.