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paleoman1234

What mineral did this wood turn to?

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paleoman1234

This petrified wood was found in Gainesville, Missouri. 

Trying to identify the mineral that replaced this wood. Also if possible, some rough idea of age.20180530_210218.thumb.jpg.c6fee8ab1a6a877e687c4ae68784f2aa.jpg

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DPS Ammonite

Most wood is replaced with quartz and related chalcedony, jasper and opal. It is most likely quartz if a metal knife blade does not scratch it.

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caldigger

Looks a bit like common opal to me. But rather hard to get a good pic over my phone.

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paleoman1234

Is it possible to be chert?

20180530_210119.jpg

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Fossildude19

Looks like chert to me.  :unsure: 

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ynot
5 hours ago, paleoman1234 said:

Is it possible to be chert?

 

1 hour ago, Fossildude19 said:

Looks like chert to me.  :unsure: 

 

It is a quartzite but I have never heard of chert replacing wood.

Wood that is replaced with quartzite is called agatized.

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Carl

I know that petrified wood can be replaced with several varieties of quartz but I've never heard of quartzite, which is metamorphosed sandstone. And I'm not certain that piece in question is actually petrified wood - I suspect Fossildude 19 was saying that it was chert rather than petrified wood.

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ynot
1 hour ago, Carl said:

I know that petrified wood can be replaced with several varieties of quartz but I've never heard of quartzite, which is metamorphosed sandstone. And I'm not certain that piece in question is actually petrified wood - I suspect Fossildude 19 was saying that it was chert rather than petrified wood.

I have been taught that "quartzite" is any silica dioxide mineral. Agate, chert, flint, aventurine, etc. and metamorphosed sandstone.

 

To Me the op's piece looks like an oxidized agate, and is right for a poor state of preservation of wood.

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Carl

Silica is the word you would use for minerals made of silicon dioxide. Quartzite is a metamorphic rock which was originally pure quartz sandstone. I'm pretty sure there is no umbrella term for these things as one is a rock and the other is a mineral.

 

And I agree that it is possible that the OPs piece is wood but I'd never feel confident IDing it as such without clear cellular structure or extremely fine external detail, like knot holes.

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Tidgy's Dad
Just now, Carl said:

Silica is the word you would use for minerals made of silicon dioxide. Quartzite is a metamorphic rock which was originally pure quartz sandstone. I'm pretty sure there is no umbrella term for these things as one is a rock and the other is a mineral.

 

And I agree that it is possible that the OPs piece is wood but I'd never feel confident IDing it as such without clear cellular structure or extremely fine external detail, like knot holes.

In geology, the term silicate would encompass both rocks and minerals that are composed primarily of silicon dioxide (plus some where there has been a replacement of some of the silica) 

I think this piece is a chert, not wood. 

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Auspex

"Microcrystalline silica", in one of its myriad forms.

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Carl
1 hour ago, Tidgy's Dad said:

In geology, the term silicate would encompass both rocks and minerals that are composed primarily of silicon dioxide (plus some where there has been a replacement of some of the silica) 

I think this piece is a chert, not wood. 

Perfect! Thanks TD.

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Fossildude19

Yeah, sorry for not being clear. I was saying I didn't think it was wood, but just chert. 

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Bobby Rico

 3 for Chet sorry not wood.

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DPS Ammonite
1 hour ago, Tidgy's Dad said:

In geology, the term silicate would encompass both rocks and minerals that are composed primarily of silicon dioxide (plus some where there has been a replacement of some of the silica) 

I think this piece is a chert, not wood. 

A silicate is any mineral with SiO4 in it and includes quartz (SiO2). It refers to copper silicate, aluminum silicate, iron silicate, silicon dioxide (quartz), etc. Use of the term "silica" refers to forms of quartz (SiO2): opal; cristobalite; chalcedony; tridymite; chert etc. Wood is often replaced/mineralized with silica while replacement/mineralization with other silicates is rare.

 

I often say that a fossil is replaced/ mineralized with silica (until I can research it further) instead of saying quartz, opal, chalcedony, jasper etc.

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Tidgy's Dad
8 minutes ago, DPS Ammonite said:

A silicate is any mineral with SiO4 in it and includes quartz (SiO2). It refers to copper silicate, aluminum silicate, iron silicate, silicon dioxide (quartz), etc. Use of the term "silica" refers to forms of quartz (SiO2): opal; cristobalite; chalcedony; tridymite; chert etc. Wood is often replaced/mineralized with silica while replacement/mineralization with other silicates is rare.

 

I often say that a fossil is replaced/ mineralized with silica (until I can research it further) instead of saying quartz, opal, chalcedony, jasper etc.

As I said, a silicate must be predominantly silica, but is not any mineral with SiO4 in it. Check on Tundrite, for example. Tundrite has 10 percent or so SiO4 but over 16 percent CO3 so is a carbonate, not a silicate.

Sometimes in a mineral, some of  the silica is replaced by another element such as in orthoclase where one in four silicon atoms is replaced by aluminium ( anion AlSi3O8) and the charge neutralized by potassium  - KAlSi3O8 . But these are silicates as it is still the dominant group.

Yes, silica includes quartz and its various cryptocrystalline (chalcedony, some chert), microcrystalline (other cherts and jasper,sometimes though that can be chalcedony or a mix as well), polymorphous (cristobalite, tridymite) or hydrated (opal) varieties. Silica thus also includes biological structures is some plants, sponges diatoms etc as well as pure glass and silica gel.  

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DPS Ammonite

A silicate must not always be predominately silica. Paraphrasing definitions from the "Glossary of Geology" by Bates and Jackson I learned that "silica" refers only to SiO2 while "silicate" refers to SiO4. My "Optical Mineralogy" book by Kerr lists silica as a silicate (broad sense). My point is that most silicates usually contain only SiO4 and not silica. 

 

I agree that we sometimes classify minerals according to their predominant components. Thus, Tundrite which contains SiO4 is not considered a silicate in a narrow sense. Thanks @Tidgy's Dad for prompting me to learn about the difference between silica and silicate and thoughtfully listening to my pedantic writings.:)

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paleoman1234

Another view of the same piece.

20180531_175319.jpg

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abyssunder

The conchoidal fractures from the first picture reminds me of chert (silex if you want), so silica rich material, while the external surface shown in picture two might be a little younger than the core. I suppose the way of the silicification process was from the inside to the outside. Also, I can't exclude banded chert or similar material.

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ynot
10 hours ago, Carl said:

Silica is the word you would use for minerals made of silicon dioxide. Quartzite is a metamorphic rock which was originally pure quartz sandstone. I'm pretty sure there is no umbrella term for these things as one is a rock and the other is a mineral.

One of the pitfalls of being self taught.

I think the best term (the one I should have used) is "cryptocrystalline quartz".

 

3 hours ago, paleoman1234 said:

Another view of the same piece.

After looking at this picture and reviewing the other pictures, I have to agree with the others and call this a chert nodule, probably not petrified wood.

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paleoman1234

Thank you for your help everyone :)

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