Authenticating quartz (?) Keichousaurus?

[Roses]

Hello! First, does anyone know what the mineral composition of most keich fossils is? The common darkly colored ones? Or does it vary a great deal?

 

I have some idea what to look for in the “normal” dark keich fossils, but this one appears to be composed of mostly quartz…? Or is it something else? 
 

This seems challenging to fake and the photos look convincing to me, but I have no experience in comparing these white keich specimens. Is this likely to be real?

[jpc]

certainly not quartz.  I don't know much about K's preserved this way, but I do know that bones are never preserved as quartz.  Bones can indeed be preserved with white coloring like this one, but is it real?  The close -up photos look pretty good, but I think someone familiar with this preservation would have a more valid opinion than mine.  

[Roses]

12 minutes ago, jpc said:

certainly not quartz.  I don't know much about K's preserved this way, but I do know that bones are never preserved as quartz.  Bones can indeed be preserved with white coloring like this one, but is it real?  The close -up photos look pretty good, but I think someone familiar with this preservation would have a more valid opinion than mine.  

I thought agatized bones, like the gem dinosaur bones people make into jewelry, were composed of microcrystalline quartz (and a smattering of other things), is that not the case? Is it just quartz filling the voids in the bone structure and the actual bone is preserved as something else?

[FranzBernhard]

1 hour ago, Roses said:

First, does anyone know what the mineral composition of most keich fossils is? The common darkly colored ones?

I don´t know, but its probably the "bone mineral" - apatite.

 

1 hour ago, Roses said:

Or is it something else? 

The dark color of fossil bones often comes from traces of included coalified material.

I am wondering, if this Keicho has been baked, thereby having the coaly particles oxidized, leaving white apatite behind. I am noticing a reddish hue of the matrix - oxidation of iron compounds during heating? Well, that´s just a wild hypothesis.

 

On the other hand, we had a thread about baked crinoidal limestone, resulting in white crinoid bits in reddish matrix (starting from more uniform grey material).

 

Franz  Bernhard

Edited December 15, 2022 by FranzBernhard

[Roses]

1 hour ago, FranzBernhard said:

we had a thread about baked crinoidal limestone, resulting in white crinoid bits in reddish matrix (starting from more uniform grey material).

I’d be interested to read it if you happen to recall the thread title - I wasn’t able to find it searching keywords. 
 

Here’s another example of a similar keich, including the red matrix. The prep is so much better than average that it makes me think the bone has been mineralized by something harder than usual, but maybe these just happen to be nicely prepped.

[jpc]

2 hours ago, Roses said:

I thought agatized bones, like the gem dinosaur bones people make into jewelry, were composed of microcrystalline quartz (and a smattering of other things), is that not the case? Is it just quartz filling the voids in the bone structure and the actual bone is preserved as something else?

I stand corrected.  Technically yes, that is quartz, but it is more commonly called agate, which is a speciefic version of quartz, as I understand it.  Agatized, is a better term than, say quartzified.    

[FranzBernhard]

10 hours ago, Roses said:

I wasn’t able to find it searching keywords.

Sorry, haven´t found it either.

 

10 hours ago, Roses said:

The prep is so much better than average that it makes me think the bone has been mineralized by something harder than usual,

That´s indeed a possibility.

I have another hypothesis: the specimens are baked before prepping, making prepping easier?

Maybe not the whole specimen is baked, just the surface layer? With a blow torch, for example? Just wild guesses.

Will start a new topic!

Franz Bernhard

[rocket]

I have got some infos from a chinese collector a year ago about this special preservation. They come from a small layer and perhaps they had been baked by vulcanism. But, never had one on my own, they are nice and unusual but little bit expensive. Chinese dealers often say the bones are "jade" so they are expensive. Hmmmm

Never seen an unprepped one, but know this kind of preservation from some german sites with permian reptiles and fishes. They are preserved in nearly the same way, not 100% but "similar". Bones are "fritted" (do not know the exact translation, means heated and baked).

Perhaps one day someone has a bad one to do thin slices of a bone.

 

[Roses]

12 hours ago, rocket said:

I have got some infos from a chinese collector a year ago about this special preservation. They come from a small layer and perhaps they had been baked by vulcanism. But, never had one on my own, they are nice and unusual but little bit expensive. Chinese dealers often say the bones are "jade" so they are expensive. Hmmmm

Never seen an unprepped one, but know this kind of preservation from some german sites with permian reptiles and fishes. They are preserved in nearly the same way, not 100% but "similar". Bones are "fritted" (do not know the exact translation, means heated and baked).

Perhaps one day someone has a bad one to do thin slices of a bone.

 

Fascinating! Is the sort of specimen you mean, from Germany? I can’t tell from the photo whether the crystallized look of the fossil is the same, but at least it’s a white skeleton on red matrix.

 

I’ve emailed a scientist who published on Keichousaurs a decade ago, so maybe he will be able to point us in the right direction

[rocket]

thats a cool one, permian from US

we have fishes and amphibians in thin-layered, grey to green-grey stones. I will look for a pic