Cleavage resistance of plastically deformed natural diamonds revealed by dissolved planar features

We describe here diamonds with planar segments of limited lateral extension, some of which have dissolved to form flat etch channels. We have documented such features only in diamonds which show otherwise lamellae of brown or pink color due to plastic deformation along (111) planes, called "colored graining lamellae". The planar segments are identified as cleavage segments. We suggest that the extension of the etch channels is controlled by the geometry of the pre-existing cleavage segments, as dissolution happens preferentially at sites offering a high available surface. These cleavage segments (indifferently dissolved as flat etch channels or not) are laterally limited by colored graining lamellae along another set of (111) planes. This indicates that plastically deformed diamond is "cleavage resistant". Further, it reveals that plastic deformation may induce different types of defects-either cleavage or colored graining lamellae-along different sets of octahedral planes in the same crystal. (c) 2005 Elsevier B.V. All rights reserved.