TUMBES, Peru – With their striking coral-colored spurs, spondylus shells were more precious than gold to the people of pre-conquest Peru and archaeologists exploring ruins outside this northern city have found a “bank” where the Inca empire stored its reserves in the forms of elaborately carved jewelry.

The team working at the Cabeza de Vaca site outside Tumbes, near the border with Ecuador, have found the only known Inca workshop dedicated to crafting pieces from spondylus.

Excavations have unearthed pieces in the shapes of birds and corn kernels as well as an Andean cross, “chacana,” that was part of noble attire in Inca times, Oliver Huaman, the director of the Cabeza de Vaca project, told EFE.

Spondylus is found only in the warm waters of the Gulf of Guayaquil, off the Ecuadorian coast.

The shells were brought to the Cabeza de Vaca complex, where they were transformed into pieces for distribution across Tahuantinsuyo – the Inca domain that extended from southern Colombia to northern Argentina.

Those treasures, like other goods, traveled via the Qhapaz Ñan, the 30,000-kilometer (18,650-mile) network of roads built by the Incas.

The shells, called “mullu” in the indigenous Quechua language, have been found at most burial sites of prominent figures of Peru’s pre-Columbian cultures.

“There’s this myth of a god who fed on spondylus at an Andean lagoon near Lima, located nearly 4,300 meters (14,100 feet) above sea level, and is called Mullucocha (spondylus lake),” Huaman said.

Rosa Maria Valverde, director of archaeological research at Cabeza de Vaca, said spondylus was also used for food offerings to the gods.

“Mullu extraction is not easy since they adhere to rocks 15 to 30 meters (50 to 100 feet) under water, which required expert divers and the use of different techniques to get the shells from the sea,” Valverde said.

Huaman said that some skulls found in the area show a callus in the area of the ear that was common among divers as a result of the effects of water pressure at great depths.