How deep is the color layer created by lattice-diffusion with titanium or chromium in corundum?

Lattice-diffusion treatment in corundum, specifically using titanium or chromium, aims to enhance the color by introducing specific elements into the crystal lattice. This process penetrates the stone to create a color layer, typically characterized by its shallow depth. The correct depth of the color layer created by this technique typically ranges from 0.01mm to 0.50mm. This limited penetration means that while the surface color appears enhanced, the overall integrity and structure of the stone remain largely intact, which is an important aspect to consider in gemstone identification and appraisal.

The other depths mentioned, such as those in different options, exceed the typical penetration depth associated with lattice-diffusion treatments, which are designed to provide surface coloration without significantly altering the body of the gem. Thus, the choice indicating a range of 0.01mm to 0.50mm accurately reflects the reality of this treatment’s effect on corundum gemstones.