How to differentiate them?
The easiest test to do is to use a magnet. Attractive, shiny metals, such as silver, gold and platinum, are non-ferrous materials, meaning that they are not magnetic. Take a piece of "silver" jewelry and place it near a magnet; if it is attracted to it, then it is not sterling silver. It is stainless steel that is highly polished to look like silver.
Real 925 sterling silver jewelry typically has certain marks on it to indicate its purity. These marks include "925", ".925" or "S925", to represent the 92.5 percent pure silver that exists. If these marks are not present, it doesn't necessarily mean that it's not sterling silver. If there is an official stamp of some sort on the jewelry, then it's highly likely that it is real sterling silver.
Sterling Silver does not rust. But it Tarnish over time. This is because sterling silver will slowly oxidize when exposed to air. this is the main reason why silver jewelry tarnishes over time and takes on a black tinge to it. These black marks are not likely to occur if it is not real sterling silver.
The price that you paid for your jewelry is a good indicator as to whether it's real sterling silver or not. 925 silver is much more expensive than alternatives. If the price you're paying for seems too good to be true, then it's likely that you're not purchasing real 925 sterling silver jewelry.
