It is a copper quarter... because quarters have been made mostly of copper since 1965. What you're seeing is the copper core, where the outer layers of copper/nickel cladding have been eaten away or otherwise somehow removed.
Ooo OK that makes since. Cause some parts look good then others look like copper. I took a eraser to it and it shined right up like a penny.
Like others stated, your coin was probably damaged either by the environment or by chemical means. Sometimes, the copper/nickel clad coins can lose their outer layer when they are cut from the roll of metal. Other times, the clad layer separates after the coin has been struck. It is pretty easy to tell the difference because a coin that has lost the clad layer after it is struck will lack some of the detail. The strike of a coin that lost the clad layer before it is struck will have very sharp details. If the defective planchet makes it through the minting process undetected, it should look something like this.
