Gold owes its dazzling lustre to the way it reflects light. But ultra-thin gold flakes can also generate and emit their own light in a process called photoluminescence.

Gold coins amassed by collector Paul Narce of Castillonnès, France and hidden in a wall have fetched nearly $4 million at a recent auction at Beaussant Lefèvre in Paris.

A newly discovered trove of gold coins found in a wall at a nature reserve in the Golan Heights, an area Israel annexed from Syria during the Six-Day war in 1967, is shedding new light on ancient ...