Video: Metallurgist Grigory Raykhtsaum shows Smithsonian three different ways to test if something is solid gold: a colour test, a thermal conductivity test, and a particle test. It’s all computerised now so all he has to do is scan the object to get a read on the colour, zap it with an electrical current to measure the conductivity and scrape a bit off to have it analysed in a powerful microscope.