Shale

We have a lot of blue shale on this place.   In some places we have little oil slicks from all that shale.   When we first moved here, I gathered all sorts of rocks from the creek to make a fire pit.    The blue rocks exploded when we built our first big fire.  

Note:  Don't use blue oil shale to line a fire pit with.

If you look at our creek banks, you can see layers of blue shale alternating with orange iron-rich layers of sedimentary rock. 

You can see the blue layer near the bottom of this pic.

The whole blue and orange thing makes me happy.

Here's a better view.

Most of the bottom of the creek bed is blue like that.   After storms have moved a lot of water through, the bottom is scrubbed clean of algae, etc and the blue shines through.