We know D.C. Get our free newsletter to stay in the know.

I’m pretty much happy to ignore this year’s Grammys completely: Kokayi didn’t win, Stevie Wonder suffered the indignity of sharing a stage with the Jonas Brothers, and I won’t even get started on the bizarre Chris Brown/Rihanna incident that took place the night before the ceremony.

But there’s one moment of Sunday’s telecast that I just can’t get out of my head.

While accepting one of the skrillion Grammys that Coldplay nabbed, Chris Martin said, “We’re not, of course, the heaviest of rock bands, you may have noticed. We’re kind of the limestone of rock bands. Not as hard, but still charming.”

Gotta love the Brits and their self-deprecating “humour,” but c’mon-limestone isn’t exactly granite or anything, but isn’t it used in the construction of buildings? If Martin is going to try to be all cute and self-effacing, he should go all out: if he wants to compare his band to a soft rock, he should really reference the softest rock known to man.

But what rock would that be?

Because my science schoolin’ ended in the 10th grade, I turned to the Reston-based U.S. Geological Survey, our country’s foremost authority on minerals and rocks, and asked for help.

I initially thought Coldplay should be compared to talc, not only because talc is extremely soft, but because I like the idea of comparing the band to one of the essential ingredients in baby powder. But it turns out that talc is a mineral, not a rock, according to Kate Johnson, program coordinator of the USGS Mineral Resources Program.

Johnson graciously indulged my geology-related music question and sent me a very helpful e-mail pointing me to a table (taken from a resource titled Principles of Engineering Geology) that lists the relative hardness of rocks.

According to that table, limestone is indeed one of the softest rocks around, second only to shale.

“[Y]ou can see that although limestone isn’t very hard, shale is even less hard,” Johnson wrote. “So, from this we can learn that although limestone is categorized as a soft rock, shale is an even softer rock.”

“Summary: the softest mineral is talc; shale is a very soft rock. But limestone is definitely a soft rock, too. Good call by Mr. Martin, I’d say,” she concluded.

So, as it turns out, Chris Martin knows a thing or two about rock—well, sedimentary rock, at least.