Calling all geologists

[Skeptic Ginger]

Figures Canada rocks would know rocks. I agree and that is what my spec is now that I have dug it out and am looking at it. Mine has obsidian basalt mixed with glassy parts and non-glassy basalt and lots vesicles though they are not as homogeneous in size and distribution. We have lots of basalt here in the West, that's for sure.

Here are some Google images:
http://history.nasa.gov/EP-95/p38b.jpg
http://seis.natsci.csulb.edu/basicgeo/EXTRUSIVE/Basalt_handspec_vesicular.jpeg

 

[Zep]

That's a pretty dense rock!

It's some slag.