Here is some more interesting reading. http://books.google.com/books?id=M8pIAAAAMAAJ&pg=PA1469&lpg=PA1469&dq=Porphyry+Copper+Deposit+milford+mining&source=bl&ots=d1udZH1TIR&sig=yGiv-ns5UO3STrLXXKtGMW-cUvY&hl=en&ei=RWIaTefPD8Tflgfg2qGDDA&sa=X&oi=book_result&ct=result&resnum=3&ved=0CCwQ6AEwAg#v=onepage&q&f=false http://www.palladonmining.com/s/PressReleases.asp?ReportID=94384&_Title=Palladon-Ventures-Ltd-Continues-Geophysics-and-Drills-Chalcocite-Blanket-at... http://en.wikipedia.org/wiki/Copper_mining_in_the_United_States