# Tell me about this rock or fossil **URL:** \ **Category:** Factual Questions\ **Created:** [March 8, 2013, 6:24pm UTC](https://boards.straightdope.com/t/tell-me-about-this-rock-or-fossil/652406 "2013-03-08T18:24:39Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![SmellMyWort](https://avatars.discourse-cdn.com/v4/letter/s/ea5d25/32.png) [@SmellMyWort](https://boards.straightdope.com/u/SmellMyWort)\ **Post date:** [March 8, 2013, 6:24pm UTC](https://boards.straightdope.com/t/tell-me-about-this-rock-or-fossil/652406/1 "2013-03-08T18:24:39Z")
This item was found about a hundred years ago by a friend’s grandfather somewhere in central WI. It is belived to be a petrified heart of some animal. Is that what it is or is it something else? Is it rare and/or valuable? I appreciate any thoughts on this item. Thanks in advance! [Photos](http://s1245.beta.photobucket.com/user/smellmywort/library/) ---
**Author:** ![Really\_Not\_All\_That\_Bright](https://avatars.discourse-cdn.com/v4/letter/r/e8c25b/32.png) [@Really\_Not\_All\_That\_Bright](https://boards.straightdope.com/u/Really_Not_All_That_Bright)\ **Post date:** [March 8, 2013, 6:46pm UTC](https://boards.straightdope.com/t/tell-me-about-this-rock-or-fossil/652406/2 "2013-03-08T18:46:27Z")
The heart is muscle tissue, so it would be highly unusual for a heart to be preserved unless the animal was mummified. I’m no expert, but I think it’s a herbivore tooth. ---
**Author:** ![SmellMyWort](https://avatars.discourse-cdn.com/v4/letter/s/ea5d25/32.png) [@SmellMyWort](https://boards.straightdope.com/u/SmellMyWort)\ **Post date:** [March 8, 2013, 8:45pm UTC](https://boards.straightdope.com/t/tell-me-about-this-rock-or-fossil/652406/3 "2013-03-08T20:45:04Z")
Thanks for your response. I’ll see if I can dig anything up on herbvore teeth. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [March 8, 2013, 10:19pm UTC](https://boards.straightdope.com/t/tell-me-about-this-rock-or-fossil/652406/4 "2013-03-08T22:19:11Z")
It looks like a fossil echinoid or sponge to me. I’ll try to find a comparable example. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [March 8, 2013, 10:34pm UTC](https://boards.straightdope.com/t/tell-me-about-this-rock-or-fossil/652406/5 "2013-03-08T22:34:41Z")
OK, how about [these](https://www.google.co.uk/search?hl=en&client=firefox-a&hs=5F7&rls=org.mozilla:en-GB:official&source=lnms&tbm=isch&sa=X&ei=WGc6Ub2pF-6Q7Abr04GgCw&ved=0CAoQ_AUoAQ&biw=1024&bih=470&q=Raphidonema%20farringdonenseRaphidonema%20farringdonense)? ---
**Author:** ![SmellMyWort](https://avatars.discourse-cdn.com/v4/letter/s/ea5d25/32.png) [@SmellMyWort](https://boards.straightdope.com/u/SmellMyWort)\ **Post date:** [March 8, 2013, 11:01pm UTC](https://boards.straightdope.com/t/tell-me-about-this-rock-or-fossil/652406/6 "2013-03-08T23:01:03Z")
> [@Mangetout](#): > > OK, how about [these](https://www.google.co.uk/search?hl=en&client=firefox-a&hs=5F7&rls=org.mozilla:en-GB:official&source=lnms&tbm=isch&sa=X&ei=WGc6Ub2pF-6Q7Abr04GgCw&ved=0CAoQ_AUoAQ&biw=1024&bih=470&q=Raphidonema%20farringdonenseRaphidonema%20farringdonense)? Thanks for the suggestion. I do see some similarites; the concave end and the hole, for example. Your examples seems much more porus than what I have, which seems to be the biggest difference. I wonder if the type of fossil you suggest is possible with a more dense rock? ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [March 8, 2013, 11:21pm UTC](https://boards.straightdope.com/t/tell-me-about-this-rock-or-fossil/652406/7 "2013-03-08T23:21:04Z")
Yes - it looks as if yours is fossilised as flint or chert. It’s quite similar to many of the flint sponge fossils I’ve seen here on the south coast of the UK - in fact, I’ve got some quite similar in my collection (although none with quite that kind of broken-up look on the outside). ---
**Author:** ![the\_diego](https://avatars.discourse-cdn.com/v4/letter/t/7bcc69/32.png) [@the\_diego](https://boards.straightdope.com/u/the_diego)\ **Post date:** [March 9, 2013, 2:12am UTC](https://boards.straightdope.com/t/tell-me-about-this-rock-or-fossil/652406/8 "2013-03-09T02:12:33Z")
It doesn’t look like an elephant’s ear sponge or similar. My own guess is some shell, whether coral or mollusk, or even a vegetable shell (nut or palm.) The original form is that dark inner layer while the lighter one is just encrusted minerals. The funny thing is the cavity should have been filled up. The nut or shell stayed closed and whole even as it was being petrified. ---
**Author:** ![SmellMyWort](https://avatars.discourse-cdn.com/v4/letter/s/ea5d25/32.png) [@SmellMyWort](https://boards.straightdope.com/u/SmellMyWort)\ **Post date:** [March 11, 2013, 3:06pm UTC](https://boards.straightdope.com/t/tell-me-about-this-rock-or-fossil/652406/9 "2013-03-11T15:06:15Z")
Another good suggestion. I’ll see if I can find any similar examples online.