# Is this a piece of fossilized coral I found in my yard? **URL:** \ **Category:** Factual Questions\ **Created:** [November 1, 2012, 9:05pm UTC](https://boards.straightdope.com/t/is-this-a-piece-of-fossilized-coral-i-found-in-my-yard/639613 "2012-11-01T21:05:40Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![JohnT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnt/32/15048_2.png) [@JohnT](https://boards.straightdope.com/u/JohnT)\ **Post date:** [November 1, 2012, 9:05pm UTC](https://boards.straightdope.com/t/is-this-a-piece-of-fossilized-coral-i-found-in-my-yard/639613/1 "2012-11-01T21:05:40Z")
[http://www.flickr.com/photos/68782016@N08/8145840774/in/photostream](http://www.flickr.com/photos/68782016@N08/8145840774/in/photostream) [http://www.flickr.com/photos/68782016@N08/8145840838/in/photostream](http://www.flickr.com/photos/68782016@N08/8145840838/in/photostream) [http://www.flickr.com/photos/68782016@N08/8145809963/in/photostream](http://www.flickr.com/photos/68782016@N08/8145809963/in/photostream) [http://www.flickr.com/photos/68782016@N08/8145810045/in/photostream](http://www.flickr.com/photos/68782016@N08/8145810045/in/photostream) It’s that last picture that really makes me think this isn’t just a rock. If it’s not fossilized coral, any idea as to what it could be? ---
**Author:** ![Yllaria](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yllaria/32/3452_2.png) [@Yllaria](https://boards.straightdope.com/u/Yllaria)\ **Post date:** [November 1, 2012, 9:26pm UTC](https://boards.straightdope.com/t/is-this-a-piece-of-fossilized-coral-i-found-in-my-yard/639613/2 "2012-11-01T21:26:35Z")
Unfossilized coral would look like that. ---
**Author:** ![Filbert](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/filbert/32/3433_2.png) [@Filbert](https://boards.straightdope.com/u/Filbert)\ **Post date:** [November 1, 2012, 10:16pm UTC](https://boards.straightdope.com/t/is-this-a-piece-of-fossilized-coral-i-found-in-my-yard/639613/3 "2012-11-01T22:16:47Z")
Yeah; looks like coral, but doesn’t really look fossilised to me. ---
**Author:** ![GreasyJack](https://avatars.discourse-cdn.com/v4/letter/g/df705f/32.png) [@GreasyJack](https://boards.straightdope.com/u/GreasyJack)\ **Post date:** [November 1, 2012, 10:24pm UTC](https://boards.straightdope.com/t/is-this-a-piece-of-fossilized-coral-i-found-in-my-yard/639613/4 "2012-11-01T22:24:50Z")
“Fossilized” isn’t really a technical term. It literally means becoming a fossil, but that can happen lots of ways, including when the original material just sits around long enough to be considered a fossil. Since the calcite or aragonite exoskeletons coral grows are readily preserved, lots of coral fossils are the original material. So the only difference between “fossilized” and simply dead coral is the age. ---
**Author:** ![JohnT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnt/32/15048_2.png) [@JohnT](https://boards.straightdope.com/u/JohnT)\ **Post date:** [November 1, 2012, 10:26pm UTC](https://boards.straightdope.com/t/is-this-a-piece-of-fossilized-coral-i-found-in-my-yard/639613/5 "2012-11-01T22:26:13Z")
> [@Filbert](#): > > Yeah; looks like coral, but doesn’t really look fossilised to me. Yeah, you’re right. :smack: ---
**Author:** ![JohnT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnt/32/15048_2.png) [@JohnT](https://boards.straightdope.com/u/JohnT)\ **Post date:** [November 1, 2012, 10:27pm UTC](https://boards.straightdope.com/t/is-this-a-piece-of-fossilized-coral-i-found-in-my-yard/639613/6 "2012-11-01T22:27:18Z")
Anyway, I found it in San Antonio, TX (over 120 miles to the ocean) and it’s been a while since there has been coral around here. ---
**Author:** ![KermitTheFrig](https://avatars.discourse-cdn.com/v4/letter/k/47e85d/32.png) [@KermitTheFrig](https://boards.straightdope.com/u/KermitTheFrig)\ **Post date:** [November 2, 2012, 2:31am UTC](https://boards.straightdope.com/t/is-this-a-piece-of-fossilized-coral-i-found-in-my-yard/639613/7 "2012-11-02T02:31:14Z")
How long since anyone traveled to San Antonio from a place where you can find coral? ---
**Author:** ![lieu](https://avatars.discourse-cdn.com/v4/letter/l/c2a13f/32.png) [@lieu](https://boards.straightdope.com/u/lieu)\ **Post date:** [November 2, 2012, 2:49am UTC](https://boards.straightdope.com/t/is-this-a-piece-of-fossilized-coral-i-found-in-my-yard/639613/8 "2012-11-02T02:49:36Z")
> [@JohnT](#): > > Anyway, I found it in San Antonio, TX (over 120 miles to the ocean) and it’s been a while since there has been coral around here. I’d have to know the locale but it well could be from the Western Interior Seaway. That’s Late Cretaceous, so probably at least 66 mya. ---
**Author:** ![JohnT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnt/32/15048_2.png) [@JohnT](https://boards.straightdope.com/u/JohnT)\ **Post date:** [November 2, 2012, 3:18am UTC](https://boards.straightdope.com/t/is-this-a-piece-of-fossilized-coral-i-found-in-my-yard/639613/9 "2012-11-02T03:18:34Z")
> [@KermitTheFrig](#): > > How long since anyone traveled to San Antonio from a place where you can find coral? Not too sure what you mean here, but I’m sure people land here every day coming from someplace that has coral…? Anyway, the coral was in a field that I’m clearing, so it wasn’t something I picked up that was dropped. ---
**Author:** ![Kolak\_of\_Twilo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kolak_of_twilo/32/73_2.png) [@Kolak\_of\_Twilo](https://boards.straightdope.com/u/Kolak_of_Twilo)\ **Post date:** [November 2, 2012, 3:20am UTC](https://boards.straightdope.com/t/is-this-a-piece-of-fossilized-coral-i-found-in-my-yard/639613/10 "2012-11-02T03:20:49Z")
How deeply was it buried? ---
**Author:** ![Zabali\_Clawbane](https://avatars.discourse-cdn.com/v4/letter/z/ecd19e/32.png) [@Zabali\_Clawbane](https://boards.straightdope.com/u/Zabali_Clawbane)\ **Post date:** [November 2, 2012, 3:27am UTC](https://boards.straightdope.com/t/is-this-a-piece-of-fossilized-coral-i-found-in-my-yard/639613/11 "2012-11-02T03:27:34Z")
Maybe the previous occupants held a funeral/burial for their saltwater aquarium that died somehow? 😕 ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [November 2, 2012, 3:28am UTC](https://boards.straightdope.com/t/is-this-a-piece-of-fossilized-coral-i-found-in-my-yard/639613/12 "2012-11-02T03:28:24Z")
> [@lieu](#): > > I’d have to know the locale but it well could be from the Western Interior Seaway. That’s Late Cretaceous, so probably at least 66 mya. Except that Late Cretaceous reefs were made up mostly of rudists, a kind of bivalve, rather than corals. ---
**Author:** ![JohnT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnt/32/15048_2.png) [@JohnT](https://boards.straightdope.com/u/JohnT)\ **Post date:** [November 2, 2012, 3:32am UTC](https://boards.straightdope.com/t/is-this-a-piece-of-fossilized-coral-i-found-in-my-yard/639613/13 "2012-11-02T03:32:58Z")
> [@Kolak\_of\_Twilo](#): > > How deeply was it buried? I had to dig it out with my hands, but not too deeply. To answer the next question, not likely as it was in an empty field. ---
**Author:** ![eschereal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eschereal/32/18939_2.png) [@eschereal](https://boards.straightdope.com/u/eschereal)\ **Post date:** [November 2, 2012, 3:40am UTC](https://boards.straightdope.com/t/is-this-a-piece-of-fossilized-coral-i-found-in-my-yard/639613/14 "2012-11-02T03:40:20Z")
The most common fossilized coral, IIRC, is called Petoskey Stone, named for a town in northern lower Michigan, which is a long way from the sea. My best friend picked up a fossilized clam in nowhere South Dakota, though it was paving gravel, so it could have come from many miles away. Much of the US used to be under the sea: you can buy sea salt that comes from southern Utah. ---
**Author:** ![April\_R](https://avatars.discourse-cdn.com/v4/letter/a/3da27b/32.png) [@April\_R](https://boards.straightdope.com/u/April_R)\ **Post date:** [November 2, 2012, 3:50am UTC](https://boards.straightdope.com/t/is-this-a-piece-of-fossilized-coral-i-found-in-my-yard/639613/15 "2012-11-02T03:50:11Z")
It looks like brain coral. Examples [http://www.paleodirect.com/pgset2/cor099.htm](http://www.paleodirect.com/pgset2/cor099.htm) > **[SALE CLEARANCE Brain Coral Fossil Organic Gemstone - Etsy](https://www.etsy.com/listing/81685730/sale-clearance-brain-coral-fossil)** > > LISTED @ 40% OFF! 39 x 28 x 6mm - 43 carats - Quanity: 1 Natural Indonesian Agatized Fossil Coral Cabochon Thank you for viewing our gemstone selection! Visit us @ http://www.etsy.com/shop/beadsaddict for a wide variety of druzy cabochons [http://www.thinktank.ac/page.asp?section=505§ionTitle=Brain+Coral](http://www.thinktank.ac/page.asp?section=505§ionTitle=Brain+Coral) You can make knife handles and gem stones out of it. Neat. ---
**Author:** ![GreasyJack](https://avatars.discourse-cdn.com/v4/letter/g/df705f/32.png) [@GreasyJack](https://boards.straightdope.com/u/GreasyJack)\ **Post date:** [November 2, 2012, 5:19am UTC](https://boards.straightdope.com/t/is-this-a-piece-of-fossilized-coral-i-found-in-my-yard/639613/16 "2012-11-02T05:19:46Z")
> [@Colibri](#): > > Except that Late Cretaceous reefs were made up mostly of rudists, a kind of bivalve, rather than corals. Two things. One, even though rudists were the most common reef-formers during the Cretaceous, reefs of that age with large numbers of scleractinian corals are still fairly common. Most of the so-called rudist reefs still had rugose corals and scleractinians well-represented, and Cretaceous-age reefs where rudists aren’t the majority reef former are fairly common. Second, the remnants of the Interior Seaway in southeast Texas and up the Mississippi embayment hung on into the Paleogene when the rudists died out. Looking at the state geologic map, it looks like San Antonio is pretty close to the K-Pg boundary, so I would expect to see mostly scleractinians anywhere to the southeast of town. ---
**Author:** ![JohnT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnt/32/15048_2.png) [@JohnT](https://boards.straightdope.com/u/JohnT)\ **Post date:** [November 2, 2012, 5:33am UTC](https://boards.straightdope.com/t/is-this-a-piece-of-fossilized-coral-i-found-in-my-yard/639613/17 "2012-11-02T05:33:40Z")
I’m on the NW side, where 1604 meets I-10. ---
**Author:** ![Omar\_Little](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/omar_little/32/269_2.png) [@Omar\_Little](https://boards.straightdope.com/u/Omar_Little)\ **Post date:** [November 2, 2012, 6:49am UTC](https://boards.straightdope.com/t/is-this-a-piece-of-fossilized-coral-i-found-in-my-yard/639613/18 "2012-11-02T06:49:11Z")
I’m guessing that someone in the last 50 years dropped it in your field, after they collected it at the beach. I have a piece almost identical to your piece that I picked up in Maui about 5 years ago. ---
**Author:** ![picunurse](https://avatars.discourse-cdn.com/v4/letter/p/7bcc69/32.png) [@picunurse](https://boards.straightdope.com/u/picunurse)\ **Post date:** [November 2, 2012, 8:20am UTC](https://boards.straightdope.com/t/is-this-a-piece-of-fossilized-coral-i-found-in-my-yard/639613/19 "2012-11-02T08:20:59Z")
I’ve bought bags of Dolomite lime as a soil additive that have had chunks that size that look very similar. ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [November 2, 2012, 10:57am UTC](https://boards.straightdope.com/t/is-this-a-piece-of-fossilized-coral-i-found-in-my-yard/639613/20 "2012-11-02T10:57:51Z")
Yeah, what other people have said - looks like brain coral, could be a fossil, could be recent, hard to say if you’re not an expert. But generally, I would not expect to find a fossil just lying in the soil, so I’d vote “recent anthropogenic erratic”. If it were really a coral fossil, I’d expect to find it in a bed of similar rocks with other corals and the like. [Next page](https://boards.straightdope.com/t/is-this-a-piece-of-fossilized-coral-i-found-in-my-yard/639613.md?page=2)