Abstract
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. This coating served to armor the coins from future chemical or biological attacks. Once coated, the coins were colonized by at least two distinct populations of gold-tolerant bacteria that precipitated abundant nanoparticulate gold in the black crust material and produced biomineralized bacteria in a web-like mat. Above this middle layer of black crust, the outer layer consisted of a geochemical reaction front of euhedral crystals of iron sulfate and iron oxy-hydroxide species, formed by the interaction of seawater with the chemical wastes of the bacterial mat. Understanding this process has application for assessing the diverse and extreme conditions under which nano-particulate gold may form through biological processes, as well as understanding the conditions that contribute to the preservation or degradation of marine archaeological materials.
Highlights
Significance of the California Gold RushThe decade following the discovery of gold in California was arguably one of the most catalytic times in US history
James Marshall is credited with the official discovery of gold in California on January 24, 1848 at the site of a sawmill he was building for John Sutter on the American River [4], though gold was known to occur in California far earlier [5,6]
Five samples of black crusts were obtained from the surface of $20 gold coins that were recovered from the SS Central America shipwreck site
Summary
The decade following the discovery of gold in California was arguably one of the most catalytic times in US history. The California Gold Rush greatly accelerated western migration by Europeans, and eastern migration by Asians and Pacific Islanders. It significantly strengthened the economy of the young United States of America, and stripped native peoples of their ancestral lands, killing up to 80% of their population [1,2,3]. There is the issue of being certain of an item’s provenance or historical authenticity The scarcity of such direct archeological and geological evidence from the gold rush period of California was significantly lessened with the discovery of the SS Central America shipwreck site, providing scientists with a trove of material as a well-preserved time-capsule from 1857
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