Thursday, January 19, 2012


When I was a kid, I was fascinated by mica. Still am, really: the world could always use a little sparkle. And on many trails in the DC area, the soil is full of little sparkly bits of mica.

Out of the trails we frequent, it seems most common on the Northwest Branch near Burnt Mills Dam on Colesville Road. Not only are the trails quite sparkly, but there are several sandy spots along the river where you can find larger pieces of mica. The paper-thin sheets stack together into chunks the size of a small rock.

If you peel off a single sheet of mica, you can observe some very unique properties: it's (somewhat) flexible, and you can see through it. How often do you get to bend or look through something that looks like a rock?!?

Photo credit: Annie in Beziers
But technically, mica is not a rock. It's a mineral: a building block for rocks. And that's how you'll most often see it: it's the mineral that shows as sparkly flecks in granite. You'll see it in rocks along the trail, and in the granite countertops of high-end kitchens.

Beyond brightening kitchen countertops, mica is prized for many uses. It is heat resistant, so it was used historically for stove windows, and more recently in space vehicles and electric irons. It doesn't conduct electricity, so it's used as a very thin insulator in electronics. Its flakiness makes it a good, sandable filler for drywall. And eyeshadow? Mica gives it its sparkle.

Where have you found mica? Leave us a comment below! And leave some on the trail for the rest of us...