What is this?

[painshill]

Yep... those are classic compression/relaxation features you can expect to see in siliceous rocks. But they are entirely natural. What we have here is essentially quartz which has crystallized in a cryptocrystalline manner from a "liquid" form (arising from extreme pressure) with some weathering. "Cryptocrystalline" means that there are crystals but too small to be readily discerned by the naked eye... and one notch up from that would be "microcrystalline". If you can see divot-like features then I would strongly suspect that they are vestigial crystal formations and the edges thereof which have suffered a little erosion... but not man-made.

[Trubke]

Thank You! Great explanation.

[gregszybala]

Thanks for the thanks Trubke! If you have questions, ask. If you have some finds your not sure of , post some pics. Good folks here and they will help you out and try to steer you in the right direction.