How much is a 1999 gold New Jersey quarter worth?

The US Mint did not issue any gold State Quarters. If you have one it ihas either been gold plated by someone other than the mint or it has simply tarnished to a golden hue. Gold plated coins are not worth anymore than the metal used to make them. A quarter that has tarnished to a golden hue may have some value to those who collect tarnished coins. Numismatically it has a value of a quarter unless it is in one of the ultra high uncirculated grades.