Need an ID, please.

[cyberwild360]

This was attached to a rock that I recently acquired. When it's closed it has a purple mat. I suck at taking pictures but this is my best try.

 

[DrBegalke]

Hard to tell from those pics, looks like it could be Galaxea sp.

 

[StephLionfish]

Vote for Green Star Polyps.

 

[SushiGirl]

It does look like a ton like a galaxea. Are you sure it has a purple mat? Can you get a pic with the polyps closed?

 

[seapug]

If it has a hard calcium skeleton with sharp protrusions its a Galaxea. If it's a rubbery purple mat it's some sort of GSP (but doesn't look like a typical GSP in the photos).

 

[GerritM]

I think it is a Briareum.

 

[SushiGirl]

I think it is a Briareum.

Which is star polyps (not necessarily green).
Wish the original poster would come back with a pic of it closed.

 

[Thisseemsfishy]

Is it encrusted to the rock?