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What is a pseudo-morph

 
 
Reply Fri 19 Oct, 2012 08:52 pm
Is petrified wood a type of pseudo-morph?
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Type: Question • Score: 0 • Views: 2,374 • Replies: 9
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dalehileman
 
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Reply Sat 20 Oct, 2012 01:38 pm
@Steve Culbreth,
http://onelook.com/?w=pseudomorph&ls=a
farmerman
 
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Reply Sun 21 Oct, 2012 09:24 am
@Steve Culbreth,
NO, (and theres no hyphen, its all one word)
Pseudomorphs have to do with a chemical weathering and replacement of one mineral by another but where the new mineral retains the crystal structrure of the former.

(This is basically a paraphrase of the definition from the DEFINITIVE SOURCE,(ie the AGI Glossary of Geology, 5th EDITION (2005), Neuendorf,Mehl, and JAckson eds)

We dont use the word "Psudomorph to describe fossils, and Petrifi3ed wood is really a fossil)"
In your opther thread, youve sorta used Pseudomorph backwards by imp[lying that a "fossil" retains the shape of the mineral genesis. Thats just incorrect usage.
farmerman
 
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Reply Sun 21 Oct, 2012 01:02 pm
@farmerman,
I tried to find some fairly neat specimens of Turquoise pseudomorphs (after flourapatite) but I wasnt able to get any neat specimen pix.
Heres the usual standard of a pseudomorph. Its limonite after pyrote.
You can see how the limonite (an iron oxyhydroxide) still retains the crystal structure of the pyrite mineral.

    http://obgrocks.com/store/images/2212_1.jpg
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Steve Culbreth
 
  1  
Reply Thu 25 Oct, 2012 05:49 pm
@farmerman,
I am using the term, used mainly in gemology, but also describes the process that affects fossils. The book, Mineralogy, by John Sinkankas, includes the same process to explain how fossils acquired the minerals, even pyrite and other metals, even uranium being injected and replacing on the electron level, with pressure and heat. starting with salt and gypsum, progressing to quartz, titanium or diamond. Unless it's in it's pure form a mineral will only micro-crystallize. around the scaffold of tissue fibers. No fossil book mentions anything about salt preservation, as the initial mechanism for the mineralization process, even when they are talking about marine deposition. Contact areas and hydro-thermal activity provide the conditions that alter everything under ground, depending on the depth and the parent rock also.
Steve Culbreth
 
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Reply Thu 25 Oct, 2012 06:29 pm
@dalehileman,
Thanks for the reference, it included fossils as used by paleontologists.
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farmerman
 
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Reply Thu 25 Oct, 2012 06:47 pm
@Steve Culbreth,
Theres a lot of stuff youve posted and some of it is correct. (I knew Sinkankas through the Museum director and head gemologist for the Dupont Collection. He was a really good gem cutter and was given free reign through the Smithsonian to write several of his populr gemology books. I think hes been dead for a decade or more)

Nevertheless, we can all do name dropping and Id bore the **** out of you;
A pseudomorph IS and only is the chemical replacement of one mineral for another.Its done as "pyrite after limonite" or phosphoapatite after psilomelane"/Tho say a pyritized fossil is a "Brachiopod replaced by pyrite" is idiotic and meaningless. Its apples and oranges. The fossil species remains the same , its only been replaced by another salt(pyrite). The term , in your quotes, may have been incorrectly used to describe fossils that hve been remineralized. However that is wrong. There is no reason to describe a fossil as a "pseudomorph" of anything since its alreadydescribed and has not changed "Species"l . Fossil remineralization is commonly siliceous and can also be several other minerals including calcite/aragonite, phosphate, flourapatite from calcapatite (usually the first step in bone fossilization, sulphate and sulfosalt etc etc)

As I read to you and I will repeat. HERE IS THE OFFICIAL DEFINITION FROM THE AGI Glossary of Geology: Ed V:

A mineral, whose outward crystal form is that of another crystal species, it has developed by alteration, substitution,encrustation, or paramorphism.A pseudomorph is described as being "after" the mineral whose outward form it has'eg quartz after flourite

In the geosciences (including paleo) we get pretty persnickety about misuse of terminology and jargon. So you may drop terms all you wish and name drop even more and the term pseudomorph does not change to suit your desires. Might I suggest that the real word you are searching for is "Petrifaction" or "petrification". Those terms, used interchangeably, specifically refer to entire "bodies" of the organism (or plant) whose substance has been altered or substituted by a mineral (like those I identified above)

A fossil is a cast, an ichnofossil, a sole mark, a mold,a C13/12 ratio cast, an alteration or a petrification. Each of those has a specific meaning to geoscientists, as does a pseudomorph.

Let John RIP, he wasnt a scientist, he was a popular writer for hobbyists and a hell of a good gem carver and auctioneer.














Steve Culbreth
 
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Reply Thu 25 Oct, 2012 09:47 pm
@farmerman,
Citing references such as books and authors is not dropping names. Without using your geo. jargon, maybe a layman can get a clue as to what you just said, I am holding out for another comment or a second opinion.
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Steve Culbreth
 
  1  
Reply Thu 25 Oct, 2012 10:40 pm
@farmerman,
Quartz after wood makes it a pseudomorph, or fossil wood. I am using the same geo. jargon to point out the reality of what used to be live tissue scraps and left-overs that were salt brinned from the Mesozoic, thanks to the dinos. That, these mineralized pieces of tissue exist, and can be gleaned of much knowledge to further the awareness of the highly intriquing life and times of T-Rex and all the other predators of that Era, is such an affront to the geodes, as I'll refer to them and not drop any names that might refer to some of my critics. At this time I actually appreciate any critic, because it gives me my own forum, thank you very much.
farmerman
 
  1  
Reply Fri 26 Oct, 2012 04:35 am
@Steve Culbreth,
Quote:
Quartz after wood makes it a pseudomorph, or fossil wood
Ive given you a definition and some direction from The AGI's own "jargon dictionary". If you still wish to be incorrect about this, I cant stop you. Just dont use it in front of a rock collector or a geologist. Its like fingernails on a blackboard.

Imagination is a great thing. It allows us to make patterns out of obscure things and it also allows us to make "Pictures in the clouds". I think youve got a case of the latter





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