Goldman Sachs Group Inc. and UBS Group AG issued another round of bullish calls for gold, with stronger-than-expected central ...

This means that if you buy 18K gold, 18 of the 24 parts will be pure gold and the rest will be a 50:50 mix of copper and silver because the purest gold is too soft to be used in jewellery.

This is the minimum amount which is required to buy "x" number of lots of a particular commodity to trade in futures market.