In the electron microscope, mercuric sulfide (cinnabar), long implanted in skin as a tattoo, and mercuric sulfide, freshly embedded in agar, were found to have similar appearances. Qualitative chemical analysis for mercury in tissue from the tattoo indicated it was present. Laser-microprobe analysis showed that material in the tattoo was identical to cinnabar embedded in agar. Selected-area diffraction studies revealed that the material in the tattoo was crystalline, and had interplanar spacings corresponding closely to those of mercuric sulfide.
Silberberg I, Leider M. Studies of a Red TattooAppearances in Electron Microscope, and Analysis by Chemical Means, Laser Microprobe and Selected-Area Diffraction of Tattooed Material. Arch Dermatol. 1970;101(3):299-304. doi:10.1001/archderm.1970.04000030043006