According to National Geographic, archaeologists discovered the dung in a mining camp last year in Israel's Timna Valley.
Erez Ben-Yosef, a University of Tel Aviv archaeologist told National Geographic he began excavating the site known as Slave Hill last year and initially thought the dung came from a goat and was just a few decades old.
However, high-precision radiocarbon dating and organic material showed the excrement and mining camp was from the King David and King Solomon times.
Ben Yosef told National Geographic:"...the [radiocarbon] dates came back from the lab, and they confirmed we were talking about donkeys and other livestock from the 10th century B.C. It was hard to believe."
National Geographic says King Solomon was very likely to have had industrial-scale mining operations because of the large amount of gold and bronze in his Jerusalem temple, as well as his extreme wealth detailed in the Hebrew Bible.