  Surfaces of natural diamonds etched in high-pressure experiments in H2O, CO2
and H2O-NaCl fluids were investigated using Atomic Force Microscopy. Partial
dissolution of the crystals produced several types of surface features
including the well-known trigons and hillocks and revealed several new types of
defects. Besides well-known trigons and dissolution hillocks several new types
of defects are observed. The most remarkable ones are assigned to anelastic
twins of several types. The observation of abundant microtwins, ordering of
hillocks and presence of defects presumably related to knots of branched
dislocations suggests importance of post-growth deformation events on formation
of diamond microstructure. This work confirms previous reports of ordering of
extended defects in some deformed diamonds. In addition, the current work shows
that natural diamonds deform not only by dislocation mechanism and slip, but
also but mechanical twinning. The dominant mechanism should depend on
pressure-temperature-stress conditions during diamond transport from the
formation domain to the Earth surface.
