Obsidian's Ghost

Mono Monday challenge. 

Overlay -   using Rocks as your main. 

Obsidian is a naturally occurring volcanic glass formed as extrusive igneous rock. My wife was given this rock specimen by a member of the Cambridge Geological Society.

Thanks for all of the lovely comments, stars and hearts from my '3 Blips from King's College' yesterday.

Thanks also to Carolina for hosting today's challenge.