My daughter and I found this stone on our beach on the shores of Lake Erie outside of Buffalo, NY. It is a smooth stone with multiple round "divots" in its surface. These 'divots' are perfect and smooth. I have included these pictures for reference. Please help us solve the mystery of this rock. What caused this? Is it common? My three year-old is asking me questions and I would like to give her some answers. Thank you!!!!
http://i62.photobucket.com/albums/h106/shezarealgem/rock1.jpg
http://i62.photobucket.com/albums/h106/shezarealgem/rock2.jpg
2007-08-10 14:32:26 · 4 answers · asked by shezarealgem 2 in Science & Mathematics ➔ Earth Sciences & Geology
To answer the question of the yellow groundmass's hardeness: yes, it was scratched by a nail just now. Thanks!
2007-08-10 14:55:59 · update #1
Thanks Foxfire. Upon inspection this one has some yellow inclusions that are still intact. Cool!
2007-08-11 03:14:26 · update #2
Hard to tell from the pictures, but a very similar question was asked a few days ago with a very similar looking rock.
To me, it looks like sandstone with limestone (calcite) concretions, and the limestone has weathered away to form the voids. Or it could be limy shell (calcium carbonate fossil) fragments that have dissolved.
If you could provide the hardness of the yellowish groundmass, it would help a lot. Nothing technical here, just let us know if you can scratch it with a nail or not (a carpenter's nail, not a fingernail!).
It's certainly not an igneous rock, meteorite, or conglomerate.
2007-08-10 14:42:36 · answer #1 · answered by minefinder 7 · 2⤊ 0⤋
It is either sandstone or mudstone that has had calcite inclusions in it which have eroded away and fallen out.
Originally the "divots" were cavities where mineral-laden water formed calcite inclusions. Then through tumbling caused by water action the outer layers of stone eroded away, and the inclusions fell out, forming the divots.
I have some that still have the calcite inclusions in them.
I hope this explains it for you?
2007-08-10 23:23:35 · answer #2 · answered by Foxfire 4 · 1⤊ 0⤋
shezarealgem,
What you have is a limestone cobble with some interesting dissolution features. As mentioned earlier, a very similar question was asked just a few days ago. Since it would take some time to retype my answer, just go to that question via the link below and read my answer. You'll find some explanations as to how features like this form.... my answer is the last one. Let me know if you have any further questions!
http://answers.yahoo.com/question/index;_ylt=AlUMtZhv6gBQCcKdYbEE2lTty6IX?qid=20070807145435AA0gN59&show=7#profile-info-UtcGr5Vtaa
2007-08-11 04:35:26 · answer #3 · answered by mnrlboy 5 · 1⤊ 0⤋
its called "calsa"
2007-08-10 15:32:13 · answer #4 · answered by rpoker 6 · 0⤊ 0⤋