Case 1, image 1: This was skin submitted around an entrance gunshot wound. This individual was shot through his tattoo. Note that the pigment is within the dermis and the epidermis is not damaged. There was no evidence of soot or unburned gunpowder in the sampled section.
Case 1, image 2: A closer look at the tattoo pigment.
Case 2, image 1: This 56-year-old man died of a gunshot wound of the chest (distant range). The skin of entrance wound is contused and hemorrhagic and has focal brown-black pigmented foreign material (tattoo ink).
Case 2, image 2: A closer look.
Forensic pathologists often sample skin from entrance gunshot wounds to look for histologic evidence of soot and unburned gunpowder deposition.
Beware. Not all darkly pigmented material is soot. You must consider clothing fibers (if shot through clothing), tattoo pigment (if shot through a tattoo), disrupted hair shafts, bullet wipe, and other bits of debris that penetrated the skin. The best way to learn is to take a section of all gunshot entrance wounds so you can train your eye.