Diamond explosively synthesized from metal/graphite mixtures in shock configurations resulting in high temperatures, moderately high pressures, and relatively long holding times at pressure were investigated by electron microscopy and electron diffraction. Particles up to 5‐&mgr; diameter consist of a matrix of 10–40 Å, variously oriented crystallites which contain clusters of randomly oriented 100–1600‐Å crystallites. Particles larger than 4–5 &mgr; are densely fused aggregates of such composite units.