“Piranha” AGATE
Surface-Treated AMBER
Unusual CERAMIC Gem Simulant
CORUNDUM: More Bulk Diffusion—Rubies and Orange Sapphire
DIAMOND with Internal Inscriptions
Two Large GLASS Imitation Jade Carvings
JADEITE—Bleached, Impregnated, and Dyed, with Unusual Inclusions
CULTURED PEARLS—With Treated Yellow Color

Featured Lab Note: Diamond, with Internal Inscriptions
Diamond inscriptions are typically created by lasering characters on the girdle surface. Recently, though, the East Coast lab has seen three inscriptions that were totally within the interior of the diamond. Two different methods appear to be responsible.

The first two diamonds had characteristics similar to those caused by internal laser drilling, as documented by S. McClure et al. (“A new lasering technique for diamond,” Summer 2000 Gems & Gemology, pp. 138–146). It is possible that the technology described in that article was a collateral effect of early experiments to place internal inscriptions in diamonds. The inscription in the top figure was placed on an internal fracture. The black letters “NE” are clearly visible. The other small internal fractures in the same area have black lines extending along their length. These black lines are typical of those associated with fractures created during the internal laser drilling process. It appears that the black lines on this fracture were controlled to create the letters.

In the second case, the number “2” is inscribed on a small fracture present in a 2.14 ct oval brilliant.

The inscription “31107345” in the third stone, a 1.01 ct rectangular modified brilliant, was also totally internal, but had a much different appearance (bottom figure). We believe ion implantation is responsible for this second type of inscription, because it is not associated with any inclusions. This is a method (also known as doping) whereby ions (charged atoms) are introduced into a solid through their high kinetic energy (see R. Kalish and S. Prawer, “Ion implantation of diamond and diamond films,” in M. A. Prelas, G. Popovici, and L. K. Bigelow, Eds., Handbook of Industrial Diamonds and Films, Marcel Dekker Inc., New York, 1998, pp. 945–982). By bombarding the diamond with atoms of either argon or boron, one can make “marks” inside the stone. The marks are actually slight deformations in the crystal lattice that scatter light, and thus they tend to show up as thin white lines. Note that the depth of the inscription is uniform, and that it is suspended a uniform distance below the surface (i.e., a few tenths of a millimeter). This can be achieved by controlling the energy of a beam of ions of a particular size.

It is possible that these three internal inscriptions were done for trial purposes, since we have seen only a limited number of them to date. However, given the apparent high degree of control in the internal lasering process, we believe such inscriptions may become more common. Internal inscriptions would have one benefit over the typical surface inscription in that they would be extremely difficult to remove. However, creating fractures in a diamond or printing letters below the surface would amount to adding inclusions to a stone, which could have a direct effect on the clarity grade.

Joshua Sheby and Vincent Cracco
GIA Gem Trade Laboratory, New York