Stromatolite

[karahbell]

I purchased this piece last year from a miner that found this near the surface in Missouri. It's quartz on lace agate on stromatolite fossil. There is a little chalcedony in there two after examining it. 

I am just learning about fossils and searched this forum for stromatolites and nothing came up (that I could find) so wanted to share this with all of you. I took some photos with a macro lens of the crystals, agate and the stromatolite. I really love examining everything with a macro lens

 

 

 

 

 

 

[Fruitbat]

That IS a beautiful specimen!

 

I do have a little information available on stromatolites in my pdf library here on TFF.  Here's a LINK to that section.  Perhaps you'll find something of interest.

 

-Joe

[karahbell]

32 minutes ago, Fruitbat said:

That IS a beautiful specimen!

 

I do have a little information available on stromatolites in my pdf library here on TFF.  Here's a LINK to that section.  Perhaps you'll find something of interest.

 

-Joe

Hi Joe! THANK YOU!!!!! What a fantastic library! I am already reading through some. love this one... GeoSociety pdf. Thank you so much! I am wanting to learn the differences in them. Since mine was found in Missouri, I figure I have to research when that area was under water to tell how old it is?  

 

I am a sucker for the layered specimens... I have another piece I will have to share later  If you have any I would love to see....  

[ynot]

It is a nice piece, but it is not a stromatolite.

The "holes" full of rhomboid impressions are where (most likely) calcite crystals have weathered out. The banded agate grew over these calcite crystals and had a growth of quartz crystals on its surface.

[Tidgy's Dad]

I agree. 

Beautiful crystals with lovely layering, but nothing that looks stromatolitic to me. 

[karahbell]

23 hours ago, ynot said:

It is a nice piece, but it is not a stromatolite.

The "holes" full of rhomboid impressions are where (most likely) calcite crystals have weathered out. The banded agate grew over these calcite crystals and had a growth of quartz crystals on its surface.

I am just trying to learn more about them, so please don't take this as an argument. I just would like to share what I have been reading and this confuses me....

Here is a study/article which mentions these types of specimens from this location in Missouri. It does mention that they are found in the digitate algal stromatolitic beds. Taking a potosi formation. https://www.geochemsoc.org/files/5314/1270/4660/SP-7_329-336_MacMurray.pdf

 

But I am still confused though, since it doesn't look like most examples of stromatolite, maybe its not then like you say. But another article mentions stromatolites taking a tuberous shape... https://stromatolites.weebly.com/morphology.html.  I was also then thinking about how my piece is hollow and all the examples aren't, then I remember reading and watching videos about herkimer diamonds and how they are mined. They find them in the bedrock in stromatolite hollow pockets. Which I still haven't seen what the inner layer looks like, but I am searching the inter webs (haha) trying to find an example now.

[ynot]

Can not open the first link, but the second link shows the classic "layering" of stromatolites.

 Stromatolites are an algae growth and do not have an even and uniform thickness of the banding and would not have cubic crystal impressions, as Your piece shows.

They have to be buried to fossilize so would not have an open space for crystals to form over their surface.

 

I hope this helps You understand why Your piece is not a stromatolite.

[Coco]

Not calcite but quartz for me (if I don't do a mistake).

 

Coco

[Plax]

I took the stromatolite to be the orange or brown, partially preserved cavity of the specimen (pic 2). the minerals being formed around limestone? that has leached away into cavities around the stromatolite. Not saying that this is so, just offering another perspective. If the pore spaces in this interior rock are shaped like crystal impressions then this view is not correct.