What's the source? The article says nothing about it, and seawater contains copper and other metal ions all by itself: https://web.stanford.edu/group/Urchin/mi

What's the source? The article says nothing about it, and seawater contains copper and other metal ions all by itself: https://web.stanford.edu/group/Urchin/mineral.html https://web.stanford.edu/group/Urchin/mineral.html