A few years ago, Valerie and I visited the Keweenaw Peninsula for a week. Whilst walking around the town of Calumet, we stopped at a store called Copper World. There we purchased a really unique Christmas tree ornament made from an aspen leaf that had been covered in copper. Leaves are collected in the autumn each year and dried. They then are put in an acid bath that eats away everything but the veins of the leaves, after which they are coated in copper. These are macro shots of the veins on the ornament we purchased. It remains one of my favorite Christmas tree ornaments.