What is this thing I found in the tidepools?

December 19, 2018 3:03 PM

I found an unusual rock type thing in the tidepools, and I've never seen anything like it before. What could it be?
posted by BuddhaInABucket to Science & Nature (9 answers total)

Looks like some fossilized shells.
posted by entropone at 3:16 PM on December 19, 2018

is it frangible?
posted by The otter lady at 3:17 PM on December 19, 2018 [1 favorite]

Looks like a chunk of coral.
posted by jclarkin at 3:19 PM on December 19, 2018 [2 favorites]

Response by poster: It's not brittle, it's pretty well cemented together. In case it wasn't obvious from the link, there are two pictures-- the back side looks different from the front and it doesn't look like coral to me, though I could be wrong.
posted by BuddhaInABucket at 3:22 PM on December 19, 2018

Oolitic limestone (or coquinite or some other sedimentary rock type?)
posted by spamandkimchi at 4:30 PM on December 19, 2018 [2 favorites]

I think you might want to make this anonymous, as you may have broken federal laws if you actually removed this from a tide pool)
posted by MountainDaisy at 4:40 PM on December 19, 2018 [3 favorites]

The backside looks like styrofoam.
posted by jbenben at 6:25 PM on December 19, 2018

Coral skeleton. The flat parts are the back side where it adhered to the rock, when it was alive.
posted by Anticipation Of A New Lover's Arrival, The at 6:48 PM on December 19, 2018 [6 favorites]

It's a zooanthid skeleton. (A kind of coral.) I have these in my saltwater aquarium, captive grown. Please don't take them out, it's bad for the ocean plus it's home to a multitude of small animals which will now die if they're unlucky, or hurt you first by stinging or poisoning you, if you're unlucky. Cool story, people have brought live coral home only to find that it's inhabited by things like Blue Ring Octopi, which can bite and kill you in twenty minutes. No known cure!
posted by Jubey at 10:02 PM on December 19, 2018 [8 favorites]