The curious case of the Gua Made green masks

About ten years ago a collector of ancient Indonesian art contacted my husband and me to ask our opinion on a group of masks cast in an odd green metal in his possession. Some of these masks, he said, had been recovered from an underground temple in a remote site called Gua Made, north of the Brantas River in East Java. I was immediately sceptical, and became steadily more so when the collector announced that ‘the masks are more than 3,000 years old’. This date was based on thermoluminescence (TL) analysis of a terracotta brick from the ‘underground temple’. Assuming a temporal association between the masks and temple, the collector went on to propose that both could be the produc