ICBC Standard Bank just made a huge bet on gold. Although the details weren't disclosed, China's largest bank now owns one of just seven secret gold vaults hidden in London in what is something of an exclusive gold market. Here's what you need to know. A piece of the action China's ICBC is the world's largest bank by assets. And according to the BBC, China accounts for roughly 25% of global gold demand. So clearly, ICBC needs to be involved in the gold trade in a big way. However, China isn't the world's hub for gold trading; that distinction goes...