The 16 to 1 mine is famous for these strangely colored gold specimens, and it turns out that the patina is in part due to a bit of copper present, and mixed in with, the gold. This is an unusual effect in nature, gold being the noble metal and notoriously difficult to get to alloy in nature. Yet, here we have it, and with a very fine color as a result, sort of a more bronzey-gold hue. From an old gold country collection purchased from a family, several years ago. Mass is 66 grams (2 troy ounces plus a bit). Of this, most of that mass, at a guess 85% or more, is gold.