Abstract Thursday - Mystery surface

This is my entry for Abstract Thursday. I have disguised it with a simple filter - but what is it? Could it be the surface of the moon, or something seen through an electron microscope, or something much more commonplace? 
All will be revealed tomorrow!

Thanks to Ingeborg for hosting the challenge.

Update 03/05/19 The original shot is now in the extras. It is a shot of a large rock. Madwill gets the prize for being (almost) correct - in that it is a single rock rather than rocks.