A diamond cluster includes a core and an overgrown region containing a plurality of diamond crystallites extending outwards from the core, the majority of the crystallites having a cross-sectional area which increases as the distance of the crystallite from the core increases. Generally, at least 80% of the crystallites have a cross-sectional area which increases as the distance of the crystallite from the core increases. Furthermore, a method of producing a plurality of the diamond clusters includes the stops of providing a source of carbon, providing a plurality of growth center particles, each comprising a bonded mass of constituent particles, producing a reaction mass by bringing the carbon source and growth center particles into contact with a solvent/catalyst, subjecting the reaction mass to conditions of elevated temperature and pressure suitable for crystal growth, and recovering a plurality of diamond clusters from the reaction mass.
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