Pure silver is a soft metal and it is not used in making jewellery. Because it is so soft, it wouldn’t tolerate everyday wear and tear. In order to strengthen it up and make it usable for jewellery, it is combined with other metals in which it is hardened and becomes more durable.
Sterling silver jewellery is made up of a combination of 92.5% pure silver and 7.5% copper.
It is also impossible to identify sterling silver naked eyes. The only way of telling is by having it tested scientifically in a lab.