anthracite

Do you know it? (I imagine Carly does).
Anthracite is the most highly metamorphosed form of coal -a fossil fuel formed by heat and pressure over millions of years on vegetation deposited in ancient shallow swamps. It contains more fixed carbon than any other form of coal and the least amount of volatile matter. It's the least plentiful form of coal and is found mostly in the eastern United States of America.

And it is a handsome and perfectly dark, cool grey.