Etch pits and trigons on diamond: II

Some experiments on artificial etching of diamonds are described. Etching in steam and chlorine at temperatures of around 800°c produces etch pits in 'positive' orientation (i.e. opposed to that of natural trigons). Wet hydrogen in the same temperature range and above gives inconclusive results. Etching in this medium may be greatly accelerated by the presence of some catalyst. Diamonds heated in fused kimberlite at about 1450°c develop sharp-edged triangular pita in 'negative' trigon orientation. The bearing of this observation on the natural history of diamond is briefly discussed.