EVERETT — Work on the new Courtyard by Marriott hotel ground to a halt Nov. 13 when the construction workers struck something. Something big and hard.

“It was a big thud,” said Ben Hansen, the site superintendent for Halvorson Construction Group, the contracting company building the hotel for developer Touchstone Corp.

The thud came from a rock bigger than an SUV, roughly 18 or 19 feet long, 10 feet high, and weighing about 300,000 pounds. The work crews broke several drill bits on it, and even the crew’s Hitachi 450 excavator can’t lift it.

“I can roll it downhill!” Jon Bates called out from the excavator’s cab.

Given that the boulder is about 30 feet below ground, where the crew was digging out what will become the hotel parking garage, that’s not very useful.

At best guess, the rock could be up to 2 million years old, Hansen said.

“I don’t know that it’s truly 2 million years old, that’s speculation,” said Kurt Merriman, a geotechnical engineer with Associated Earth Sciences in Kirkland who was called out to the work site Wednesday morning to examine it.

The boulder is called a “glacial erratic,” basically a giant rock carried to its current location by the crest of the most recent glacial period, about 18,000 years ago, and dropped when the glacier started to retreat.

“We see this occasionally in the glacial soils that underlie the area,” Merriman said.

He thinks the boulder probably originated in northern Canada or Alaska.

In the meantime, the Halvorson crew has been working on figuring out how to get it out of the hole, and what to do with afterward, so they can get back to work.

The crew has two options, Hansen said. One is to try to break it into smaller, lighter pieces. The other is to give it to the city, for historical purposes.

“It’s a prehistoric rock,” he said. The city hasn’t gotten back to them on their offer, he added.

“They might be willing to donate it to us or work with us if we can find a home for it,” said Meghan Pembroke, the city’s communications director.

She added that a decision hasn’t been made.

Chris Winters: 425-374-4165; cwinters@heraldnet.com. Twitter: @Chris_At_Herald.