silver

Biles - the world's most decorated gymnast - won three gold medals, in the all-around, vault and team events, as well as floor silver.

A hoard of gold and silver Roman coins dating back to the reign of Emperor Nero have been found during building works in Worcestershire.

The 26 year-old was driving a silver Transit van when it went through the windscreen.

But if there is a silver lining, Snow says development tools are becoming more accessible and opening the door to smaller teams with "ingenious" ideas.

For example, they can add conductive nanoparticles, such as silver or gold nanorods, which are critical to stretchable and wearable electronics.