Granitic rock with a gray-green crustose lichen growing on it.
Porpidia albocaerulescens?

This crustose lichen caught my eye while out walking today. I was especially taken by the dramatic apothecia, those dark gray spots outlined in a very dark gray. Unfortunately, I didn’t bring my hand lens with me, so I couldn’t take a good close look at the apothecia. But here’s what they look like when I blow up the photo:

Close-up of the above photo, showing the cup-like apothecia a little bit better.

I believe this lichen is Porpidia albocaerulescens, which is sometimes called the Smoky-eyed Boulder Lichen. However, identifying crustose lichens accurately seems to require a rock hammer (to get the sample off the rock) and a chemistry set (to carry out the chemical tests used for identification).