Petrified wood or just Schist?

[Nat006]

12 hours ago, FranzBernhard said:

Thanks!

 

What does the microstructure look like? Is it grainy like sandstone or more even-wavy like chert/flint/agate?

 

Franz Bernhard

 

 

Overall the microstructure looks and feels more even-wavy. The only part that looks a bit "grainy" are the mini brown crystals on top. But in the areas where it is not covered in the crystals, it looks pretty even and smooth. It does NOT have a very-smooth, waxy feeling, it is more like solid and sturdy, but even. 

[Nat006]

[Nat006]

[FranzBernhard]

Thanks for the many pics! Still no definitive opinion.

 

The "sparkles" - are these quartz crystals or biotite or - ?

 

Franz Bernhard

[paleoflor]

Thanks for the additional photographs. 

 

This certainly looks like petrified wood.

I would not be surprised if this comes from one of the German brown coal mine deposits around Zwenkau (Saxony, Germany).

See for example this specimen, or this one, or these.

 

 

 

 

 

 

[Rockwood]

29 minutes ago, paleoflor said:

Thanks for the additional photographs. 

 

This certainly looks like petrified wood.

I would not be surprised if this comes from one of the German brown coal mine deposits around Zwenkau (Saxony, Germany).

See for example this specimen, or this one, or these.

 

 

 

 

 

 

So, it's easier to explain why some of it doesn't look like wood than to explain why some of it does? 

[paleoflor]

On 8/12/2024 at 9:38 PM, Rockwood said:

So, it's easier to explain why some of it doesn't look like wood than to explain why some of it does? 

 

Not sure if this was indeed a question directed at me, but yes: I think your summary above is a fair assessment. 

 

For me, the internal structure perpendicular to the overall "layering" (see for example yellow arrow in picture below, but note it occurs in several of the photographs) is quite hard to explain in terms of a tectonic foliation or other metamorphic/deformation feature (I guess fibrous veins can also have an internal structure that is perpendicular to the overall vein orientation, but other aspects do not fit very well with a vein option). On the other hand, such a perpendicular structure can readily form on a wood tracheid template. The existence of sections of the specimen that look less like wood may be explained by variation in the preservation quality (not very high here for sure) or perhaps even partial recrystallization of the microstructure. It is always difficult to judge from photo, of course, but I would certainly lean towards wood, especially since the piece shares quite a few characteristics (the covering of quartz crystals, for example) with petrified wood from a well-known locality in Germany.

 

Hope this helps clarify my earlier message, which in retrospect did perhaps not provide enough argumentation.

 

[M Harvey]

I am 100 % in the wood camp.

[hemipristis]

On 8/12/2024 at 7:53 AM, Nat006 said:

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I cannot tell:  are the dark lines that are near-perpendicular to the "layering" shadows or cracks?  If cracks, possible tension gashes?

[hemipristis]

On 8/12/2024 at 5:13 PM, FranzBernhard said:

Thanks for the many pics! Still no definitive opinion.

 

The "sparkles" - are these quartz crystals or biotite or - ?

 

Franz Bernhard

I was thinking the same earlier, and made the assumption that they were micas, either muscovite or biotite

[EMP]

I’ll throw my hat into the wood ring. The grain size is too coarse to be slate, a metasandstone or graywacke doesn’t make sense with the amount of foliation that’s clearly visible and it doesn’t look mylonitic either to me but I’m not an expert.