Seafloor image of gold from the shipwreck of the SS Central America. Note the formation of black crusts on the coins and some of the gold bars. These crusts appear black to grey in the image, due to constraints of seafloor lighting. Image courtesy of California Gold Marketing Group.

Black crusts that formed on gold coins recovered from the 1857 shipwreck of the SS Central America played a key role in their preservation in a near original state. Within a few years of the sinking, the significant quantities of iron and steel on the shipwreck produced laminar geochemical precipitates of fine-grained iron minerals on the coins. Th…

large mid-ship paddle wheel and other distinctive features were the first signs. However, confirmation was provided when they observed that the seafloor was littered with gold, in an area that became known as the “garden of gold” (Figure 2). The excavation that followed took four summer seasons to recover over 1,900 kg (two tons) of the lost gold. …