rock has dark blue color inside?

[smilodon]

Anyone know why some rock has dark blue color inside? I used some like that before but this time I want to figure out what exactly causes this.

 

[Jay Hemdal Verified Community Expert]

Anyone know why some rock has dark blue color inside? I used some like that before but this time I want to figure out what exactly causes this.

IDK - could it be from a skeleton oh Heliopora/blue coral?
Jay

 

[Lemons]

Anyone know why some rock has dark blue color inside? I used some like that before but this time I want to figure out what exactly causes this.

I actually just found some myself!

 

[Brit’s Fish]

Looks like Blue Ridge coral skeleton to me.

 

[Jay Hemdal Verified Community Expert]

I actually just found some myself!

Yep - Heliopora coral skeleton.

Jay