🔎 UNIDENTIFIED What is this cylindrical growth found inside quartz?

[Grldpp]

So I recently cracked open a cobble of quartz and came across this odd formation of crystals. Any idea what this is? I continued cracking to see if there were more and there quite a few throughout the rock. This is probably the best example. Some of the other examples had completely filled the cavity, others only had a very thin, less developed column through the middle. All of them have the same cylindrical cavity with a cylindrical growth growing perfectly up the middle. Any insight would be greatly appreciated!

 

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[Red-Coat]

Welcome to Tnet.

That's very cool. What it most resembles IMO is an Archimedes Bryozoan, preserved in a quartz deposit.

 

[Grldpp]

Welcome to Tnet.

That's very cool. What it most resembles IMO is an Archimedes Bryozoan, preserved in a quartz deposit.

View attachment 2133956

They do have a very similar shape to them. The question is would it be possible for them to form in quartz? I think they are typically preserved on limestone.

 

[Red-Coat]

They do have a very similar shape to them. The question is would it be possible for them to form in quartz? I think they are typically preserved on limestone.

It's an unusual preservation, given that crystalline quartz deposits are more usually igneous than sedimentary but there's absolutely no reason why sedimentary quartz cannot be the matrix and replacement mineral for a fossil.

This, in a quartz-rich cobble, is also believed to be an Archimedes bryozoan, although far less impressive than yours.

One other thing you might like to check is that what you have is actually quartz and not calcite. A hardness test and/or an acid test for effervescence will tell you.

 

[Grldpp]

It's an unusual preservation, given that crystalline quartz deposits are more usually igneous than sedimentary but there's absolutely no reason why sedimentary quartz cannot be the matrix and replacement mineral for a fossil.

This, in a quartz-rich cobble, is also believed to be an Archimedes bryozoan, although far less impressive than yours.

View attachment 2133994

One other thing you might like to check is that what you have is actually quartz and not calcite. A hardness test and/or an acid test for effervescence will tell you.

That is very cool. This rock looks very similar to the cobble I have. I am quite certain it is quartz, I just never knew it could preserve fossils like this!