Also known as base metals, non-precious metals are widely available and include stainless steel, copper, brass and bronze. Non-precious metals tend to oxidise, tarnish or corrode easily when they are exposed to air or moisture. However, they do have an advantage over precious metals: they are often significantly harder – and, because they are less rare, they are also more affordable, so they can be alloyed with precious metals such as gold to make the resulting blend more durable and affordable.