Any ideas what may have been the cause for this 1999 nmm to have this color? For a comparrison I have added a 2004, both are circulated. The top one is the one in question. The reason for such a close-up is due to the file size restriction. I dont have a scale.
Just typical toning (oxidation) from copper plating exposed to the elements. All Lincoln cents will experience this toning unless they are kept high, dry, and handled with due care. Remember, the old cents (before 1982) were 95% copper, 5% tin and zinc and cents minted afterward are now 99.2% zinc with only .8% copper (20% lighter). However the plating of post 1982 cents are still pure copper. Copper itself is VERY reactive to a number of elements including oxygen (hence the oxidation) and sulfur which forms copper-sulfate. Copper sulfate is dark in color.
Normal. I've already seen pennies in the 2002 and 03 range that look worse than that. Depends on where it's been. To bad they can't tell you where they've been.
If you've got a pencil and a popsicle stick....you've got Roy's famous do-it-yourself scale Won't tell you the weight, but it will tell you if the coin in question is off weight.
Actually Copper Sulfate is not normally available. It almost always has to be made. CuSO4 comes from an abundance of O during formation. In our air there is SO and SO2 from Sulfur burning coals at factories and power stations. The SO and/or SO2 combines easily with moisture, H20 (H 0H actually) to form the Sulfurus Acid, not Sulfuric, that causes corrosion on many things. On Copper coins, pipes, etc. it leaves a greenish residue (corrosion) that is caused by CuS03 and/or CuS04 if sufficient O is available. If corrosion on a Copper coin is not green it is not from Sulfinating.
