This is?

[strgazr27]

I hadn't noticed this on one of my rock pieces until last night. I added an actinic ReefBrite strip and suddenly I saw this. I have no idea what it is but the color under the strip is amazing. Almost seems to pulse at times. It looks hard, almost calcium based but at the same time has a smooth surface.

Any idea what this could be?

 

[knugenx]

Pavona coral a.k.a. cactus coral, potato chip.

 

[strgazr27]

Thanks! Pretty Cool..