High-magnification microscopy (10x–100x or greater with dark-field or fiber-optic lighting) reveals internal features that fingerprint a gem's origin and history. Natural inclusions might include mineral crystals, healed fractures with fingerprint patterns, or growth zoning. Synthetics often show wispy veils, curved lines, or flux residues.
Treated stones display rounded or melted inclusions from heat, residue in fractures from filling, or color concentrations from diffusion. Photomicrography documents these features for reports. Inclusion study remains one of the most powerful non-destructive identification tools.