Where the mineral-rich groundwater of the archipelago meets the tidelands, the dissolved copper it contains is processed by copper oxidizing bacteria that thrive in the brackish mud. The brownish-green film these processes create can be harvested and refined into usable material. Underground, these byproducts accumulate into deposits of various natural copper alloys much like bog iron open_in_new .

The characteristics of these deposits vary depending on the inclusion of nearby minerals, meaning that sea copper from different locations is prized for different uses. Two particular alloys that are both fairly common and of great interest are variations of bronze open_in_new ——for its increased hardness and durability——and cupronickel open_in_new , for its corrosion resistance, especially in marine uses.