A method of distinguishing between amalgam and graphite in tissue

The clinical and histologic appearance of amalgam and graphite tattoos are similar; both appear as dark particles, although amalgam, after degradation, displays a characteristic binding to blood vessels, nerves, basement membrane, and fibers. Graphite particles also consistently exhibit a light yellow peripheral birefringence under strong polarized light. Amalgam particles may exhibit a similar birefringence, but often it is weak or absent. When histologic sections containing particles exhibiting birefringence are treated with 10% ammonium sulfide solution, graphite is unaltered, whereas the birefringence of amalgam particles, if present, is changed to orange, or the particles undergo dissolution.