Scientifically, it’s called “metagraywacke.” Broadly speaking, it’s a type of sandstone.

But D.C.’s official rock, Potomac bluestone, is a metamorphic material you can actually find all over the city — in places like the White House, Tidal Basin, St. Albans School and the focus of today’s episode of “Matt About Town.”

In 2026’s first “Matt About Town” episode, back adventuring in the region, we’re digging up fun facts about the stone that was named the official rock of D.C. by law in 2014-15.

It’s a backstory that began 550 million years ago, when there were still volcanoes off what would become the D.C. coastline.

Tune in to see why this natural attribute, a swirling mix of colors that literally laid the foundations for the nation’s capital, is another hidden gem that makes the D.C. region a one-of-a-kind place.

Hear “Matt About Town” first every Tuesday and Thursday on 103.5 FM!

If you have a story idea you’d like Matt to cover, email him, or chat with him on Instagram and TikTok.

Check out all “Matt About Town” episodes here!