Jewelry Hints, Tips and Tricks: What is the difference between gold plated, gold filled and gold jewelry?

Gold jewelry finishes and their differences

Real or fine gold jewelry ranges in purity from 42 to 100 percent purity. The higher the purity of the gold the softer the item will be, therefore, gold jewelry is usually not made from 24kt gold. Most fine jewelry today is made with 14kt gold. The gold is mixed, most often with copper, zinc or silver which are non-reactive metals in their pure forms so gold jewelry is
considered hypo-allergenic for most individuals. There are some lower grades of gold that are mixed with nickel and can cause reactions by those who are allergic or sensitive to it. In some instances "white gold" is created using nickel, as well.

24 kt = 100 percent
22 kt  =91 percent
18 kt = 75 percent
14 kt = 58 percent
12 kt = 50 percent
10 kt = 42 percent

Gold Filled jewelry is 10 or 14 karat gold that has been bonded to a metal core of silver, brass or copper with high heat and pressure.The minimum amount of gold that an item can be and still be considered gold filled is 20%.  The plating on this jewelry can be cleaned like real gold jewelry so long as you are not overly harsh with it. Polishing it will not cause the base metal to be exposed. It is also hypo-allergenic for most individuals the same way pure gold is and filled metal is much more valuable than plated because the layer of precious metal is much much thicker than that on plated metals. 

Vermeil jewelry is jewelry that is made from sterling silver that has at least 10kt gold bonded over the sterling via electronic bonding. The gold must be at least two and one half (2½) microns or approximately 1/10000th of an inch of fine gold. 

Gold Plated jewelry is fine gold that is bonded either chemically or electrically to the base metal core which can be made from silver, copper or brass.1/1000th to 3/1000th of an inch is the standard layer used when gold plating is layered onto base metals.
This layer is very thin-so thin it may chip, tarnish or wear off over time exposing the base metal the item is made from below the surface of the plating. One must take care when cleaning this type of gold item for the same reason. 
Because gold is such a soft metal the plating process allows a more durable item to be created that will not bend or break in the way that pure gold can. It is not considered hypo-allergenic like real gold.