[CanopicJar (OP)]

I found this rock on vacation and had to bring it back with me!  What is it?

Thanks,

Travis

[RD]

Possibly grey outer layer is "vesicular basalt"  [?]
the holes (vesicles) are caused by gas bubbles when the basalt was molten.

The basalt has coated another type rock so is a "basaltic intrusion"  [?]

[ [?] these are uneducated guesses, but may be of help]

[Bass]

My guess is some sort of concretion in limestone?  Can you scratch the outer rind with a knife?

[CanopicJar (OP)]

It does not seem to scratch with a flat blade from my multi-tool.

Here are some additional shots.







FYI, this rock was found on the Slate Islands, which were apparently created from a meteor impact.  It is also home to the world's largest shatter cone:





and...



Travis

[RD]

This bulls-eye mark may have been made by a limpet.

[Bass]

In that case, I suspect the rock may be psuedotachylite (interior is an impact breccia clast).

Nice photos, by the way.

[RD]

Bigger vesicles in cross section...

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http://mountainbeltway.wordpress.com/2010/04/09/holey-basalt/

[CanopicJar (OP)]

Thanks for the help!  The trip to the Slate Islands was an amazing trip.  Every time you turned a corner on the beach, you ran into different types of rocks.