Nets of -Hybridized Carbon Atoms

A second type of diamond (hexagonal lattice or isodiamond) having a crystal structure similar to wurtzite is less common and slightly more energy-rich owing to its eclipsed bonds (boat-shaped 6-membered rings) as in iceane. 

The synthesis of artificial diamond from graphite requires elevated pressure (about 54 kbar), high temperature (1500°) and catalysts (transition metals) as reviewed earlier [2,16-20 cf. also item 4.1 below. 

---