Gold: Gold has physical properties conducive to jewelry. Pure gold is highly corrosion and oxidation resistant. Gold only discolors and pits from alloys used in its manufacturing. Gold dissolves in only a few solutions to include Chlorine bleach, and selenic acid water.

Silver: The abundance of silver has made it less valuable than gold and platinum in today's market. Silver has a few properties such as tarnishing that make it less desirable than gold and platinum for jewelry. It is also more difficult to work with because of its higher melting temperature and easy malleability.

Silver Purity:
Coin Silver - must have 90% silver with a 10% copper alloy
Sterling Silver - must be at least 92.5% pure
Mexican Silver - usually contains 95% pure silver with 5% copper
Britannia Silver - must be at least 95.84% pure

Platinum: Melting temperature is 1755C or 3190F.  Platinum commands a higher price in today's market,  because it is more rare than the other two precious metals.  Platinum has become a valuable commodity with  jewelry  in only the last hundred years or so, and because it does not oxidize, The National Bureau of Standards uses platinum as standards against other weights.

Palladium: Palladium, along with platinum, rhodium,ruthenium,iridium and osmium form a group of elements referred to as the  platinum group metals (PGMs). PGMs share similar chemical properties, but palladium is unique in that it has the lowest melting point and is the least dense of these precious metals. Palladium is also tarnish resistant and resistant to chemical erosion as well as intense heat. Standard alloys contain 950 parts of  palladium to 50 parts of other metals.

Make sure all jewelry purchased is marked with purity numbers!