The Maker's Mark

A finished ingot tells a story about its manufacture and value. The sunken area in the center of the top of the ingot resulted from the shrinking of the gold as it cooled; the center shrank more than the sides because it took longer to cool. When molten gold is poured into a mold, other minerals in the gold dust combine to form glass on the surface. Ingots often carry marks from hammer blows used to remove the glass.

The ingot's rust-coated surface is the result of the corrosion of the steamship's enormous engines and boilers. The gold itself does not corrode; the rust is only a surface deposit.

Ingots Decoded

The missing corner shows that an assay sample has been cut for chemical analysis. The assayer would have cut the other corner for his commission.

$3,000 TREASURE BOX

After 130 years resting at an ocean depth of 7,000 feet, these $20 gold double eagles are in nearly mint condition. The pine box is just as it was found on the wreck site of the S.S. Central America. Its remaining bottom and two sides are pocked with holes made by deep-ocean shipworms, a kind of clam. The box was made to hold 150 coins in two rows of five stacks, with fifteen coins in each stack. To prevent tampering, the joints between the boards would have been sealed with wax.

THE EUREKA BAR

This is the largest surviving assay ingot from the California gold rush period. It weighs 30 kilograms (80 troy pounds). Its worth in 1857 is stamped on the bar—$17,433.57.

It sank, along with three tons of gold, in the hold of the S.S. Central America. If it had reached New York, it would have been melted down and then minted as United States gold coins.

Ten miners would have worked for three years to gather enough gold to make the Eureka bar.