Brass and bronze are two closely related copper alloys widely used in products of all kinds, from lamps to furniture. Brass is an alloy of copper and zinc, bronze of copper and tin. Of the two, bronze is the harder metal and has been in use far longer, beginning at least 5,000 years ago. It even has a historical era named after it: the Bronze Age. Brass was not discovered until 1,500 years ago, in part because the key ingredient, zinc, rarely is found adjacent to copper deposits. Both brass and bronze are valued for resistance to damage from friction, such as in locks and doorknobs, as a material in plumbing applications, for musical instruments and as decorative elements in furniture and accessories. Brass, when polished, will appear bright yellow, similar to gold. Bronze has a reddish-brown sheen.