This story appears in the May 2017 issue of National Geographic magazine.

Crime scene investigators are about to get an assist from the land of the pharaohs. New research has shown that a pigment called Egyptian blue, formulated some 5,250 years ago, can be used as dusting powder to detect fingerprints on complicated surfaces.

The earliest known synthetic pigment, Egyptian blue is found in some of the paint that still colors ancient statues, coffins, and tomb walls. Modern scientists were intrigued by this long-lasting tint and figured out its chemical components decades ago. More recently they discovered that it emits near-infrared radiation when exposed to a certain kind of light. Researchers have now demonstrated the forensic potential of that rare, invisible luminescence.

After a crime is committed, police may dust relevant surfaces with a powder of a contrasting color. The powder sticks to the unique features of any fingerprints, providing visual proof that an individual was there. But prints may be hard to pick out on a shiny or highly patterned surface. That’s where Egyptian blue can make a difference.

The pigment is brushed on as usual. But the surface is then photographed under a white light with a modified camera and a filter sensitive to near-infrared rays. If fingerprints exist, they glow clearly in the resulting image.