Workers at 528 Pontius Ave. North found the tusk about 1.5 stories down and immediately stopped digging and roped off the area pending confirmation.
Experts from the Burke Museum of Natural History and Culture were called in to examine the find.
“Burke Museum paleontologists have examined the fossil and we are confident that it represents a tusk from an ice age mammoth,” Christian Sidor, curator of vertebrate paleontology at the Burke Museum of Natural History and Culture, said later Tuesday.
“Because the fossil is on private property and does not seem to be associated with an archaeological site, it is up to the landowner to decide what they would like to do with the tusk,” Sidor said. “We are happy to excavate the fossil if the landowner would like to take that step.
“The discovery of a mammoth tusk in South Lake Union is a rare opportunity to directly study Seattle’s ancient natural history. As a public repository, the Burke Museum would be pleased to curate the tusk and provide access to scientists and others wishing to study it,” he said.