Blue Sponge inside live rock

Paulip

New member
I may be wrong in calling it a sponge It could be crystalline. Here goes:

When you break a piece of live rock, it is often times white in the center because of calcified life forms which built up the rock. Some live rock will have a bluish color inside. Looks like a soap stain. What is that?

Here is a picture. See the white edge of this broken up rock.View attachment 16633
 
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