Just a Interesting Rock?

[minnbuckeye]

Here is a rock that I have had in my basement since summer. It has finally made it to Forum members to voice their opinion on. I know it is NOT a rugosa coral (a joke for those who saw my previous ID request). I am thinking possibly a stromatolite? Or because of the karst topography in the region, it may be a type of flowstone from a cave. Or maybe one of those rocks to put out in the garden. 

 

The bottom of the specimen: 

 

 The top: 

 

 Side views:

[minnbuckeye]

Another side view:

 

  

 

 Finally, an interesting spot to check out:

[abyssunder]

It reminds me of tufa.

[ynot]

It does look like a tufa.

[Tidgy's Dad]

Lovely! 

It's a rugose coral.

Just kidding, i think it's an algal thing. 

[Rockwood]

Can you give us any information that might be helpful in determining if it is an eroded fragment of a larger mass or just a small (colony sized) ball ?

[minnbuckeye]

1 hour ago, Rockwood said:

Can you give us any information that might be helpful in determining if it is an eroded fragment of a larger mass or just a small (colony sized) ball ?

 

@Rockwood, I believe this was found in a stream bed as is. I have walked many miles of streams around here and haven't seen this type of rock. But after reading up on Tufa, it makes sense that ground water flowing through our Karst topography dissolved the limestone, making a solution high in carbonates. As a result, Tufa instead of stalactite! Would some tufa just be a form of flowstone in a cave situation? 

 

 "Tufa is a variety of limestone formed when carbonate minerals precipitate out of ambient temperature water. Tufa is sometimes referred to as travertine. It should not be confused with hot spring travertine."   Wikipedia

 

Mike

[Bronzviking]

It has botryoidal clusters possibly calcite, which are found in Tufa deposits.

[abyssunder]

40 minutes ago, minnbuckeye said:

Would some tufa just be a form of flowstone in a cave situation? 

 

" In Central Europe's last post-glacial palaeoclimatic optimum (Atlantic Period, 8000-5000 BC), huge deposits of tufa formed from karst springs.[citation needed] Important geotopes are found at the Swabian Alb, mainly in valleys at the foremost northwest ridge of the cuesta; in many valleys of the eroded periphery of the karstic Franconian Jura; at the northern Alpine foothills; and the northern Karst Alps. On a smaller scale, these karst processes are still working. Travertine has been an important building material since the Middle Ages. " - Wikipedia, Travertine

[Rockwood]

2 hours ago, abyssunder said:

, huge deposits of tufa formed from karst springs.[

Had a feeling it would come in bulk.