Platinum jewelry is rarely 100% pure platinum. Usually, the platinum is mixed with similar metals or non-precious base metals. Generally, the higher the percentage of pure platinum, the higher the value of the jewelry.
Metals used in platinum jewelry usually fall into one of three categories:
other platinum group metals (palladium, ruthenium, rhodium, iridium, osmium)
base metals (copper or cobalt, for example)
If you want to buy platinum jewelry, find out what percentage is pure platinum, and if the item is: