Favourable conditions for getting good yield of diamond (density of graphite and diamond are 2.3 g/ml, 3.5 g/ml).

Since, graphite is themodynamically most stable allotrope of carbon, graphite to diamond is endothermic ;Given density of graphite < density of diamondWe know,d ∝1VSince density of diamond is less than graphite, good yield of diamond is obtained at high pressureSince graphite → diamond is endothermic, good yield of diamond is obtained at high temperature.