What is the difference between sterling silver and silver-plated jewelry? quora.com

Sterling silver is a mixture of pure silver and other metals added to make pure silver more durable and less soft for jewellery making. Most often, Sterling silver has a purity. 925, meaning that it contains 92.5% pure silver and 7.5% copper plus other metals (usually copper, aluminium or zinc). Its fineness thus is 925/1000. That is also the reason why it is stamped with "925" somewhere on the jewellery so it can be recognized and distinguished from silver-plated jewellery. While making silver jewellery it is important to add other metals into pure silver so that it doesn't lose its form.